Its possible it was not included when you re-contracted even though its free. This does seem to happen.
Please check to see if Caller Display is switched on by entering the code * # 234 #. If it's active you'll get the message Caller identity will be displayed.
If not, you can order it yourself online, and it will get re-activated within 24 hours.
Welcome to the Community and thank you for posting. @Keith_Beddoe has posted some good advice. It sounds like the Caller Display might not have been added when the re-contract order was placed.
Give the spets posted by @Keith_Beddoe a try and let me know how you get on?
Thank you Keith and Paddy, just reordered it. Hated not being able to block the nuisance calls ...cheers both of you!.