Why do I have to be Penalized for upgrading to a Higher Plan

Good day

Last month May 2019 I upgraded my data contract cell number *** to a much higher Plan, but today on the 8 of July 2019 realized that is never enough because my kids are also using it , I went to a Telkom shop in Wonderpark mall request to upgrade to uncapped Plan but I was told I will be panalized for almost R3000 If I upgradeto a much more higher Plan, I am really disturbed about this because I taught I i spend more the company will do good , but this is not the case you get Penalized for switching the Plans even if your contract is a Month old, Telkom must help me to switc to a Plan that will cover may family without a penalty, Please help