Mr. Price service? Does not exist.

My father took out a contract for a cellphone that ended in may. Middle may someone contacted him and asked if he wanted to renew the contract. He said no. Middle June same thing happened and he said no again. Now they keep on taking money from his account every month and phoning him every day for more money. They are a very rude bunch. My father can't speak English as he is very old. Every time I try and handle the matter they are very rude. I am his daughter and can speak English. I just want to know what can we do about this matter?