Forfeiture if one only do a upgrade when Telkom say upgrade is free

Today I got my account with an R 621.90 Contract Forfeiture added on. I was on a 24 month contract with Telkom on the 14th month I went to Alberton to upgrade for a 2 meg line to an 4 meg uncapped. They said the upgrade is free only the subscription will be different like( R 426.00 R 599.00). They changed the contract no, but it still state period now 14 to 24 months. What is the forfeiture for…..