CHANGE OF PAYMENT DATE

I phoned Autopage on 17 and 18 Feb regarding change of payment date from 15 to 25th of each month. Spoken to Mercia, Marceya, Marvin, Jess and Craig on these dates. The cell phone was blocked and then activated again after these several calls. They assured me that the payment date has been changed to 25th of each month. Today I received a SMS again that they will cut my cell phone. I phoned and spoken to Petunia who told me that she will send another request. Do I have to complain and requesting this each and every month for the changing of payment date. I am not satisfied with this after begin a customer for many year. Please help...