Very poor service

Very very poor service, I canceled the simcard and other services offered when I opened the account.I was still billed for minutes and data which I never used nor received, could not understand why my my credit is not going down but I was paying, until I viewed my statement,they very Quick to call all day everyday when you owe on the account but very slow to resolve problems they caused. Now they won't refund on the account for something I never used.