Iphone 5, Perdendo Sinal (Losing Signal)

Question

Bom dia, estou com um grande problema, estou com um iphone 5 64GB que foi comprado através de um anúncio que ví na internet, marquei com a pessoa e testamos tudo, acontece que o aparelho é importado e não tem NF, e estava tudo funcionando na hora, voltei para casa e estava normal, durou apenas algumas horas, pois o aparelho de forma aleatória, cai o sinal da rede e fica em tempo variável "BUSCANDO.." leva em torno de 30 minutos a 1 hora para voltar ao normal, fica algumas horas funcionando e acontece o mesmo problema, "BUSCANDO.." as vezes acontece de hora em hora. Não consigo mais contactar a pessoa que me vendeu.
Acontece que procurei tudo sobre EMEI, BLACKLIST, e não consegui chegar a uma conclusão, o aparelho ao inserir seu Nº de série no site da Apple, leio a mensagem : Desculpe-nos, mas este é um número de série de um produto que foi substituído.
Já testei Claro, Tim, Nextel, todas acontecem a mesma coisa, vamos aos fatos, se fosse problema de EMEI ou BLACKLIST o telefone poderia funcionar tantas horas seguidas sem apresentar problemas ? Pois quando está com sinal funciona tudo, Dados, VOZ, SMS.
Já resetei inúmeras vezes todas as configurações, já restaurei o iphone, passei grafite no chip, tentei "N" coisas.
Caso fosse algum problema da antena ou outro componente ligado a recepeção de sinal, porque funcionaria tantas hora e de forma aleatória apresentaria esse problema ?
Sou do RJ, e tem uma loja APPLE oficial aqui agora na BARRA, estou pensando em levar o aparelho ainda essa semana e tentar explicar isso, mas acontece que estou meio cabreiro do status desse aparelho, e fico com medo de eles bloquearem meu aparelho permanentemente e eu em conseguir mais usá-lo.
Ví também que tem muitas pessoas com seu EMEI bloqueado sem motivo algum.E outras que ao colocar o chip da OI funciona todos iphones 5 sem problemas, alguma alma nobre para tenta ajudar ? A única solução de imediato é tentar colocar um CHIP OI para testar a ocilação de sinal, e caso não, teria que levar a própria loja apple.
Grato, e aguardo respostas.
Good morning , I have a big problem , I have a 64GB iPhone 5 that was purchased through an ad I saw on the internet , marked with the person and test everything that happens the machine is imported and has NF , and everything was working at the time , came home and was normal , lasted only a few hours , as the machine randomly drops the network signal and is variable in time " SEEKING .. " takes around 30 minutes to 1 hour to get back to normal , is a few hours working and the same problem happens , " SEEKING .. " sometimes happens hourly . I can not contact the person who sold me .
It turns out that I sought all about EMEI , BLACKLIST , and could not reach a conclusion , the apparatus when entering your Serial on Apple's website , read the message : Sorry, but this is a serial number of a product that was replaced .
Have tested course , Tim , Nextel , happen all the same, here's the facts , if problem EMEI BLACKLIST or the phone would work so many hours without presenting problems ? For when is it works with signal , data, voice , SMS .
Have reseted all settings numerous times since restored the iphone , I graphite on chip , tried to " N " things .
If it was a problem of the antenna or other component connected to recepeção signal , because it would work so many hours and randomly present this problem ?
'm RJ , and has an official APPLE store here in BAR , I'm thinking of taking the set later this week and try to explain it , but it turns out I'm kind of suspicious of the status of this device , and I'm afraid they block my device permanently and I get to use it more .
Also saw that many people have locked their EMEI algum.E no reason other than to put the chip HI 5 iphones all works smoothly , some noble soul to try to help ? The only immediate solution is to try to put a CHIP HI to test the oscillation signal , and if not , would have to take the apple store.
Grateful, and I look forward answers .

Answer 1

Hello there, ckhapple.
The following Knowledge Base article offers up some great steps for troubleshooting cellular connection:
iPhone: Troubleshooting a cellular data connection
http://support.apple.com/kb/ts3780
Follow these steps for help troubleshooting cellular data issues on your iPhone. After performing each step, please test to see if the issue is resolved.
Toggle airplane mode: Tap Settings, turn airplane mode on, wait three seconds, and then turn off again.
Restart your iPhone.
Make sure that your software is up to date:
Check for a Carrier Settings Update: Tap Settings > General > About.
Check for an iOS Software Update: Tap Settings > General > Software Update. 
Note: Some updates may require a Wi-Fi connection.
Remove the SIM Card and reinsert it. Allow the iPhone to acquire the network again.
If your SIM card has SIM PIN enabled, try turning it off: Tap Settings > Phone > SIM PIN.
Try another location. If a different location works, but the original location still doesn't, contact your carrier to report the issue.
Reset network settings: Tap Settings > General > Reset > Reset Network Settings.
Restore the iPhone as new.
Contact your carrier to:
Verify that the iPhone is properly set up on the account with the appropriate, current data plan.
Verify that there are no account-related blocks.
Find out if there are specific error messages in the carrier logs that could help determine why the issue is occurring.
If none of the above steps resolves the issue, contact your carrier, make an appointment at an Apple Retail Store, or contact AppleCare to troubleshoot further.
Thanks for reaching out to Apple Support Communities.
Cheers,
Pedro.