incorrectly billed

i recently did a upgrade with vodacom on line and i was told that i do qualify for an uprade on line, i got my phone it was ok. On the 3rd of February i got the statement stating that and amount of R268.00 will be debited into my ok and i thought ok, my new upgrade i am suppose to pay R468.00. On the 03.03.2015 i got another statement saying that and amount of R568.59 will be debited into my account and is coulding understand so a phoned vodadom call center on spkoke to Thembisile 14.03.2015 she says the reason that they are going to debit that amount is that my account is in arreas for one month wich is totally rediculus as i always pay my account on time in need somebody to sort out this mess or i am returning their phone i will get it somewhere where they offer a better service not ripping customers.