Welcome to this user forum.
Possibly the change has caused caller display to be removed by mistake.
See if its still enabled
Is the facility switched on?
If you've ordered Caller Display check it's switched on by entering the code * # 234 #.
If it's active you'll get the message Caller identity will be displayed. If the facility isn't active then activate it using the code * 234 #.
If its not, then it can be added free of change using this link.
BT Privacy and caller display, is near the top of the options on that screen.
It takes about 24 hours to re-activate.