About cancelling ATT prepaid wireless

Hi, me and my wife are using AT&T prepaid service from long time, I m on 65$ unlimited plan and my wife in 50$ plan. I recently noticed that its 45$ for new customer. So, I am planning to cancel my existing number and get a new one. Is it possible in this way and will I be eligible as a new customer? Otherwise I am planning to change the carrier. Since AT&T is not giving any good scheme for existing customer.

Thanks