False information reveived from telkom via sms

On 14 December I received a sms from telkom mobile advising my contract is due 29 December 2017 to upgrade. When I came into the store to upgrade they said my contract is due only in end march 2018. They refused to do the upgrade. Are they now selling false information. And if they send an sms by error. Why am I to pay for their mistake. What can I do in this case