Why, Should i keep calling o2 for the right tarif selection

I've my contract extension some days ago, my number which is ended with 347, I've been offered O2 S boost tarif, with 3 GB for 14,99 EUR, at first the tarif was not changed, second I called them on the support phone to fix that, to find that they did a mistake for the 2nd time, and only offered 2 GB.

I don't have soooo much time to keep talking to you and every time has something wrong done, please for this number change the high internet speed to 3 GB as offered for the 14,99 EUR !!