AT&T GO Phone Vesta Continue to charge for service after cancellation Internet

Cancelled the AT&T Go Phone by calling there customer service department on about December 1, prior to the automatic billing scheduled for December 7.  They disabled the phone on this same day, even though they told me it should work until December 7.  Just opened my credit card statement on December 15, and they have continued to bill me for the plan.  I called the credit card company to dispute the amount.  Also called the number on the credit card for the merchant that was listed as Vesta.  When I called here, they said they have no record of the phone service being disabled.  Basically they have two companies, one (AT&T) that handles the customer service and enabling and disabling of the phones and Vesta who does the billing for them.  They do not apparently have communication between the two companies.  At first Vesta, the billing center offered to credit me the amount of the last billing, I then accepted this offer, we now had a valid contract.  Next, since I told them that I had also disputed the charges, they attempted to revoke the previously arranged contract, so in effect they have committed a breach of our verbal contract.  Spoke to several other people at both AT&T customer service and Vesta who were unwilling to help me.  I will say the customer service folks at AT&T were very professional and attempted to help, but the folks at Vesta were very short, inpatient and unwilling to help me resolve this overcharge. This is an extremely frustrating experience that has literally wasted hours of my time and caused me personal suffering having to deal with this lack of integrity or at a minimum miscommunication between AT&T and Vesta.