Careful of MTN check your statements they stole money off me

MTN has not only cheated but over billed me, and changed the terms of the contract and refused to refund, Instead sent their debt collectors to cheat me more money with threats. While they owe me. After realizing that im not backing down they admitted to owing me but a portion thewn later admited but made more deductions without consent. Now they refuse to rewfund those funds even while stating they will pay back. Instead change statements contantly.