More instalment

I have a problem with vodacom , I have a contract with them an amount of R200 and m getting paid weekly and the agreement was to pay on the 1st of each month now they add charges on my instalment in december I paid cash at celucity on the 16 for month end of december now on the 1 of january they try to deduct but the was no funds so now I must pay a penalty fee which the instalment was paid befre month end , I did try to phone vodacom but no help with my account and I did go to vodacom store the guy there told me nothing wrong to my account and I did ask them who will pay the penalty fee and he told me to call vodacom, month end of january they try to deduct again to my surprise the amount was R508 that they were trying to deduct but there were funds that could cover their instalment but the debit order bounce because they try to deduct more which is I dont understand when I check the balance for February month end its R600 its no longer R200 but m paying them every month cash the money that I did sign with them , but now my statement is a mess I need to apply for a loan but I cant because of their debit orders , and I need vodacom to clear my account and resolve this debit order issue and I did try to call vodacom since last year , last year they told me that they did remove the debit order to my account I can pay at nedbank or vodacom stores .