Unnamed Person is Linked to My Prepaid Phone

Support Team:

I own and use an Alcatel 510a prepaid phone.  Recently, someone has been tapping into my inbound service.  The charges are minuscule (for some reason). I received generous credit for these inbound taps yesterday, but I remain concerned about the intrusion, and my phone's inability to accurately record what has been happening.  My address book shows several mysterious entries, all labeled Unnamed, but not formatted the same way as past Unnamed calls.  Past Unnamed calls always included phone numbers. These new Unnameds are without any phone number; instead of a phone number, all that appears below the phone icon is an asterisk, nothing more.  My only clues involve the initial phone log, notifying me of my phone charges. With this is a phone number, which is almost equivalent to mine, except for its last four digits. In other words, the number shown has the same area code and three-digit exchange as mine.  Reviewing my Usage History, I noted that only my Alcatel phone number is listed related to the intrusion calls, rather than mystery number that had been displayed as part of my AT&T account notification log. Unfortunately, I don't remember the last four digits of mystery caller's number.  When first receiving these calls, I assumed them to be prospective clients -- until witnessing the other elements of this trespassing.  oops.  Along with the suspicious phone numbers and Address Book Unnamed entries, my phone also somehow received  a series of numerals and one dash, resembling the code an AT &T customer might use to access voicemail (as in: xxx-x).  I copied that code (or whatever) down in case it's significant and/or helpful in resolving this strange interlude.  I also tried to access my voicemail using the mystery code, but to no avail.  Perhaps the trespasser would be more successful.    ?  

By the way, I keep my phone on a level surface, and am careful not to inadvertently hit any outward initiating buttons when checking for calls or text messages.  Besides, don't forget about the inbound evidence (phone number, access code, asterisk).

Any ideas?  I'd like to block this trespasser.  Is there free anti-spyware or other AV programs made for my pre-paid Alcatel 510a that you'd recommend?  What should I do?

Thanks.  Sorry for this lengthy post.  I hope it's not too perplexing.  

--jjb