Numbers in Phone app are not correctly aligned

Living in Belgium and calling a domestic cellular number, the number has to be aligned like this when entering: 0495 66 66 66.

Since we've been in London for six days, my phone app does something weird. When I enter the same phone number it's aligned like this: 049 5666 666.

Once I press the green dial button, it's correctly aligned in the next screen.

When calling a domestic number, it's not necessary to enter the country code (+32 in Belgium), so a lot of numbers are not stored like that in my contact list.

Dialing such a number always leads to the message "number assistance". Calling is done well, but the number assistance is a proof of a wrong setting. I've never had that before our trip to London.

The phone seems to think he's still in England, but I can't find the right settings. I changed nothing while in London. GPS options are all on.

I installed iOS 17 last weekend, no solution.

Where's the hidden setting?