Sign out of Discovery+ but make sure you're signing in using the correct log in details.
Once signed in, go the account section and it'll show how it's being billed.
For instance, if it's being billed through Sky or another content partner or method. If it's showing as billed through Sky, I'd imagine you'll need to call Sky.
If it's showing as being billed by another content partner, you'll need to speak with them to get them to release the billing.
