Wi-Fi calling issue on iPhone SE (2022) with O2 network at work

I had an android phone on O2 network and were I work there is no phone signal. My android phone worked fine with wi-fi calling at work on the work wifi network.

I recently switched to an iphone ( 2022 SE) and wifi calling will work perfectly on my home broadband but will not work at work.

I contacted the IT dept and they tried to help but could not figure out what is wrong. they said they had a few other iphone users that had teh same problem but also some iphone users that had no issues with wi-fi calling (not sure how many of the no problems if any are on O2).

Anyway it is the fact it works fine with same sim and account on android but not on iphone, what does iphone do differently compared to android ? (its not the account settings 'cos it works at home)

[Re-Titled by Moderator]