Got a 24 month contract when i asked for month to month

In 2017 mtn phoned me regarding the end of my contract. I asked for month to month. Now that i want to upgrade to a new phone i cant because according to mtn im on a 24 month contract and not a month to month. The copy of the contract is ambiguous as the only place i could have seen that they issued a 24 month is through a code. How must i as a customer know what mtn codes mean?!