Entering phone numbers

Hello,
Often when making reservations, flight or hotel, I am asked to enter my phone number.

Since carrying my cell phone abroad it should be no problem reaching me on it but when entering phone number I can not enter the country code and the +, like +33 following the phone number.

I learned you have to dial 010 before the country code in Japan, would that be an idea to put in like that?

Try leaving out the + or the +33? Since you must be entering your country somewhere as part of your home address, that may not be necessary.

Just thought if there were any type of practice in Japan when entering phone numbers like that.

For domestic numbers (for which the system tends to be initially designed) usually we would just start from the area code, so that would be what I would try.

Not a problem limited to Japan, but normally you have a country of residence field and that fills in the gaps.

So +12 34 5678 9012 would just be 034 5678 9012 and the booking system would add the country code and then when dialing would drop the leading zero etc etc

I have some accounts where I cannot load in my correct phone number here in Japan so I use a default number that I have active for that country. (And occasionally I have to swap SIMs to get the correct messages I get sent . . . . .)