VERIZON WIRELESS RIPOFF Demanding Full Month Payment Even Though Full Month Not Due...Not Under Contract dallas Texas

 I did not renew my contract w/Verizon wireless, and was a customer for more than 12 years...I switched to AT&T due to better pricing, which Verizon could not meet.  ATT&T ported my phone numbers on 3/1/2013, and subsequently cancelled w/verizon on the same day... I have spoken with customer service who said I probably owed around $37. for the days of use since I was not under contract, and would get confirmration in the mail for final payment...when I received the final payment it was for the entire $114. which included the remaining days of the month I did not use verizon service.  They are insisting that I have to pay the total amount...and are now having a collection group call me.  Should I just go to the state regulatory group?  Anyone who has had any success...I would appreciate your input.  Thanks