MBD THE ****S

My Vodacom account was handed over to them last year around August, then i started paying as per arrangement. In January this year i was given a discounted offer to settle my account which i paid by end of February without hassles. While awaiting for a settlement letter i was told that i have to pay R1842.00 as they made a mistake when calculating outstanding amount. I paid the amount on the 1st of April, for the sake of removing a default on the ITC.I get a call on the 28th telling me to pay R386.00 again. What Fu###ry is this? I can't get credit anywhere because of their selfish interest