Free Apple tv+ 6 month trial

[GillP1]

Hi all, I received an email offering a 6 month free trial of Apple tv - I tried to get this a few times, but kept getting to a request for a payment card, so chose not to continue as I didn't want the subscription amount to be charged to my card. I googled it, and Apple advised to enter the card details, which I've now done. However, it's now telling me I have a 7 day trial instead of a 6 month trial! Any ideas how I can get the 6 month trial again? Many thanks!