Vodacom accounts

My husband upgraded his contract in April 2019. The contract amount including handset installment were supposed to be R1258.00 per month. When my husband spoke to a Vodacom representative he said that for the first three months the account will be R1500.00 because of the previous handset installment that had to be paid off. My husband has paid that for two months and then suddenly the account was R2058.44. The new amount for this month is R1900.00 He tried to phone them, but was sent from one department to another and finally he ended the call out of frustration. His account number is I*** and his cellphone number is ***