No email or sms notifications

Vodacom, i have been a loyal customer for a really long time, i decided about 4 months back to not renew my contract as i was out of work and times were really tough, i called you guys and instructed it to be stopped. Just before my contract expired i got a job and asked the agent over the phone that i wish to continue it, he said he'll instruct "i think" the accounts department. Unfortunately it seems, whatever the reason may be, it did not continue and i had to go onto prepaid which i was fine with. I then received my final bill which i made absolutely CERTAIN to ask the agent over the phone that there is no other hidden amounts which he confirmed, and i paid the R139.67. I then received another call on Saturday at 8h11 that there is an outstanding amount of R541.19, 4 months later. Because of this, and it having a negative reflection on my credit rating i will be moving over to another network. The network i am with should advise me of any outstanding amounts, if i cannot be contacted via phone, you have my details to send me an email or an sms, which in this case was not done. Payment has been made for the outstanding amount.