After first selecting your retailers when are you able to change them. I have contacted curve three times now with no reply.
Are you on Blue, legacy Black, subscription Black or Metal?
I am on the blue card
In that case the answer is never. Retailers are only valid for 3 months (introductory offer), after that they expire (so no more cashback). But you will not be able to change them during (or after) those 3 months.
More info here
thanks, in that case I will have to get either black or metal subscription.
When you subscribe to Black or Metal support will be able to reset your retailers (so you can choose them again). But as of yet your retailers also will be just valid for a limited time (3 months), but that might change:
My understanding was the it doesn’t reset even when you upgrade - the introductory offer is an introductory offer…
This was the case (at first), but this has changed. Check the opening post in the updated January Launch FAQ topic:
"What will happen to my Rewards/Cashback programme?
You can stay on your current programme or request to restart the 90 days period. New customers signing up will have access to the 90 days introductory offer."