Amounts springing out after Settlement quote paid

Had a call to request for early settlement, received and settled R2285. Called Vodacom was happy to be ruled as prepaid customer, and told the settlement letter is on its way. Then received an email later saying I owe them R339, then when I called I was told I now am contract 2 weeks back and forth, so to cut the abuse I paid the amount they demanded, then asked I asked again for the letter, I am told I actually owed them R660, so I need to pay again R339.00. Honestly, I am tempted to pay it so they go off my back forever, I am just not however sure if this is indeed the last amount I am paying or if I am going to be strung along this way. Its sad that we have to be serving customers in this way, considering the current circumstance. This looks like an error that they wouldn't own up to on their side.