Bill querie

Please help me MTN billed me 1600 the first month for a premium of roughly 350 per month and I went to their store to seek for assistance and the consultant assured me that the matter was resolved as I charged off data rates. The second month they charged me again 1500 having spoken to their consultants for numerous for couple of times and the problem is still consistent and their billing me for something I did not consent for so please assist with this matter