Poor cellphone service

Bigworld mobile also going by bluelabel connect gives the poorest service ever. I have a contract with them where i did complain that the device is still under warranty but its not working. I wrote numerius emails to complain about the matter. I also wanted to know how long there is still left on this contract because i want to cancel it. Iam paying for a product which i cant use. Now this month they went and took 3 payments from my bank. I went to the bank today but they cant assist me at all. When i took out the contract i specified that they must take payment month end or on the 1 of the next month. I am not even behind on any outstanding money.