CONSTANT FAILURE TO ACTIVATE DATA BUNDLES

Every single time that I request once off extra data onto my contract, IT NEVER HAPPENS! I have to make numerous call to the contact centre, where the consultant ensures me that they will activate it... but still NOTHING! This is highly frustrating as the data charges are very high ( out of bundle ) and I end up stuck with a bill that I would not have got if my data bundle was activated on time.