HT4623 My iPhone 5 mixing old text with new texts

Question

Can any one tell me how my text messages are being sent mixed with old messages?

Answer 1

My guess is that you are confusing "mixed messages" with conversations.  Text messages are shown with former messages to/from the same recipient unless you do something like delete the old message stream.
Here's pertinent material from the iPhone User Manual:
Start a text conversation: Tap <the note pad>, then tap <plus> and choose a contact, search your contacts by entering a name, or enter a phone number or email address manually. Enter a message, then tap Send.
An alert badge <exclamation point> appears if a message can’t be sent. Tap the alert in a conversation to try sending the message again. Double-tap to send the message as an SMS text message.
Resume a conversation: Tap the conversation in the Messages list.
Managing conversations
Conversations are saved in the Messages list. A blue dot indicates unread messages. Tap a conversation to view or continue it.
Forward a conversation: Tap Edit, select parts to include, then tap Forward.
Edit a conversation: Tap Edit, select the parts to delete, then tap Delete. To clear all text and
attachments without deleting the conversation, tap Clear All.
Delete a conversation: In the Message list, swipe the conversation, then tap Delete.
Search a conversation: Tap the top of the screen to display the search field, then enter the text you’re looking for. You can also search conversations from the Home screen. See Searching on page 27.
Add someone to your contacts list: Tap a phone number in the Messages list, then tap “Add to Contacts.”