This can be blocked by Scam Protection being enabled in My Account.
We can turn this off for you but will need to verify some security info.
I'll drop you a PM with the info required.
Please log in to My Account if you need to view or pay your bill, manage boosts and track your usage. From My Account you can also check your connection and test your line for any issues in the Service Centre.
WEAR A MASK - WASH YOUR HANDS - SOCIAL DISTANCE