Their mistake is costing me money

On application to renew my contract for a further 24 months I asked to be migrated from MTNAnytime350 to MTNMychoice200. The consultant mistakenly selected to migrate my contract to MTNAnytime200 instead.<br> On discovering the mistake the consultant has apologized but says that the correction will only take place in 3 months time, during which I will be billed for the MTNAnytime200 contract and receive the airtime allocated. This is going to be costly for me as the airtime value on MTNAnytime200 is far less than what I should be allocated under the MTNMychoice200 contract, despite the monthly charge being almost the same. According to my average usage I am likely to exceed the airtime value on this contract and will therefore incur further costs for the same average usage. I feel that this is unacceptable and that there should be a way to rectify the mistake immediately. We all make mistakes but there must be a way to fix it. 3 months at my expense is not good enough