Why ask me to upgrade only to tell me I cannot upgrade?!?

I received an email that states:

" Given that your internet usage is clearly on the rise, we want to offer you the opportunity to do something you never get to do - change your plan in the middle of your contract!

That’s right, you now have the opportunity to upgrade to a higher data plan, without any cancellation fees, device fees or change in your contract period."

When I app**** for the upgrade, the call center agent told me I can only upgrade at the end of the contract. When I queried about this email I had received, she told me it was a "system error" and there are no middle upgrades of contracts.

Why advertise it on your website then too?!? Is the call center agent just to lazy to help or are Telkom's marketing department really messed up???