Poor Customer care service delivery

I was on a 24 month vodacom contract and on a monthly debit order as set up in store. Vodacom had a challenge with the last debit for some reason. They failed to contact me to communicate this and it has been a good few months since the contract term was surpassed. I suddenly receive a harassing phone call from their collections attorney to say that I have been handed over and should pay with immediate effect. They have not sent me any statements of where my shortfall was or proof of their attempts at getting a hold of me. Thy know how to get hold of me to market their promotions with such ease. I am with Telkom for almost 6 years and never encountered this type of disrespect for me as their client. Vodacom you have done this the last time round and I want other to know of how I have been treated.