updating mobile number on Endessa

[JUD]

There are 2 boxes , it won't accept a mobile without a country area code in the first box .

[Malcolm]

There is no area code with a mobile so you don't have a 0 to drop.

[JUD]

Trying to enter my English mobile into my contact details for Endessa.
It will accept the UK code +44 but not my mobile , any ideas please . I have tried variations of 0044 or dropping the 0 from the mobile but no joy. ( oddly enough it will accept my landline )
Thanks