Vodacom and attorney CPA rip-off

Vodacom has handed my account over. I was never advised or contacted by the attorneys but did pay Vodacom amount on the last statement they sent me. Now I'm expected to pay a legal fee equating to half of what I owe Vodacom before the account will be returned and the sim number reinstated. I was never advised the account was handed over and never agreed to pay any fees to a third party who was not part of my agreement with Vodacom and who never even contacted me.