IPhone 4 No service after jailbreak?

Okay I've had this problem for a long time now… I jailbroke my phone somewhere around may and for a month my phone was working fine. Then all of a sudden I lost service and my phone said I needed to restore so I did that. I had signal again but then a few days later the message popped up again and I restored it again, and when it happened again I restored my phone as a new one and I would still lose service. So this has been going on for a couple of months and it seems I have to restore my phone every single day. Btw my phone is locked to AT&T and I got it from their store…

It should not be the problem of the jailbreak, take it to fix in the store.