How to Prevent Duplicate Telephone Numbers

Question

Hello
Is there a way to prevent an employee from capturing duplicate telephone numbers? Right now we have the situation where an employee can capture the same telephone number [phone] numerous times. My client would like to prevent that. A telephone number can only be entered once.
I tried Forms Personalization but get an error when trying to validate my code
DECLARE
counter NUMBER := 0 ;
BEGIN
IF :system.record_status = 'INSERT' THEN
SELECT count(*)
INTO counter
FROM hr.per_phones
WHERE phone_type = 'M'
AND phone_number = :cellno;
IF counter <> 0 THEN
bell;
MESSAGE ('This cell Number already exists. Please enter a Cell Number that does not already exist in the system.');
RAISE FORM_TRIGGER_FAILURE;
END IF;
END IF;
END;
Any ideas what I am doing wrong? Or a better way of doing this?
Regards

Answer 1

I forgot to mention I did a sync through iTunes, thought I followed the instructions.  This happened to me 2 years ago when I purchased a 4Gs.  That time I did it through iCloud, then the next time I did the sync through iTunes it doubled all the contacts telephone #'s.  I haven't used iCloud since.  This time I made sure iCloud was not activated. 
Need to find a better way to delete tel #'s.  I have over 100 contacts.  Going over to AT & T today and then to Apple store if needed.  Frustrated.