Someone I don't know used my details to take phones at Mtn, and after receiving messages and calls from the debt collectors I visited Mtn branch in Tubatse Crossing but now they have deducted money from my account

Someone I don't know used my details to take phones at Mtn, and after receiving messages and calls from the debt collectors I visited Mtn branch in Tubatse Crossing but now they have deducted money from my account. I submitted the affidavit that they requested and also contacted Mtn ***** line