Bad service

Vodacom deducted R949 in November from my account and when I called to find out why, they told that I have upgraded my phone contract in Nelspruit from R49 to R949, anyway I did an affidavit to state that it was not me I reside in Gauteng, I haven't received any feedback from them, I keep calling 135 with no assistance from any of their department, this is affecting my credit score & frustrating