50 gig offer for £8 a month isn't activating?

If you are an existing customer, uuu need to switch to this promotional tariff by contacting Smarty via webchat, which is open 08.00 - 20.00 seven days a week.

This is the Smarty community forum by the way, we are customers just like you, we do not work for Smarty. 

If you are having trouble with it, try a web chat with Smarty Support as they can access your account details whereas we community forum members cannot.