@Thechioraz53 As far as I can see, ITV X is not a channel but a streaming platform which is available on different SmartTVs in the UK, probably geoblocked, so that the app is maybe not available in Switzerland, which means that Swisscom can't add it. A VPN connection to an UK iP could help
https://en.m.wikipedia.org/wiki/ITVX
https://support.itv.com/en_us/can-i-use-my-itvx-premium-benefits-abroad-SJakCBhGj
At the moment, it doesn't seem that a linear additional ITV channel is available "free to air", which is a condition to be added.
https://www.lyngsat.com/freetv/United-Kingdom.html
A UK TV box you can only used in Switzerland if you have a UK IP address.
added: I checked the Swiss App stores, ITVX is not available in CH.