Telkom Mobile LTE - Contract Issue

I signed a 24 month Telkom LTE (10Gb) LTE contract in August last year which I decided to migrate to an 20Gb option in May of 2015. Due to some administration \blunder"my contract got converted to 36 month without the migration to 20 Gb. Apparently the Telkom call centre don't deal with migrations and I've been to the store five times without the problem being resolved. The frustration is the store cannot fix the problem them self"