Dial assist setting on iPhone

I am experiencing an issue which may be related to the ‘dial assist setting ‘ or other on iPhone .I own a iPhone which is was purchased in France and I use a French provider / carrier.

I travel regularly to the UK and use the phone whilst there.

In the past I have never had any issues dialling numbers in the uk . Especially the direct dial option via Google maps ,internet etc

However during my current visit Whenever I dial a number (e.g.use the direct dial connection option after an internet search for an address )the telephone does not understand the correct dial code to prefix the number with.

(the French dial code is 0033 and the UK is 0044.)

So when in the UK and

dialling a number as described above with ‘dial assist’ set to off , the phone will attempt to ring that number without the 0044 code and doesn’t connect .

However if I switch on “dial assist “ it will then attempt to dial the number prefixed with a dial code .but it uses the INCORRECT French 0033 code in stead of the UK 0044.

and therefore is again unable to connect.

The only way to successfully make a call is to manually dial. The number with a 0044 code……

in fact I don’t even comprehend the need for a country code as the I phone is roaming on UK networks

and As mentioned previously this has not been an issue in the past and everything worked smoothly .

In general settings the region is set to UK

and in App Store

thank you in advance for any assistance