Thanks for your post and welcome to the forums. It's great having you on board with us in the Community.
Apologies to hear about this. Usually the leaflet will hold details on how to get the deal. Sometimes when calling, the teams are not able to do flash offers and so they assume they are for new customers.
If you get any new advertisements, make sure you follow the guidance if you want the deal.
Kath_F Forum Team
Wishing you a very Merry Christmas and a Happy New Year!