Vodacom bad service and making peoples credit bad

A ***** upgrade was done on my contract after many phone call I gold hold of the ***** department in Cape Town and muliple e mails they said the problem was resolved.I then stoped the contract and since then it was quite till about 4 weeks ago and now suddenly I owe them a huge amount.There is a major lack of communication between the departments.And every time you call you get a differant call centre operator and the process just stops there.And now vodacom has gone and blacklisted me and handed me over to debt collectors.I am discusted with their way of assistance and follow up.I am on the last straw going to go and see my laywer,this is unacceptable.Please adive or give assistance.