What is the acess code when dialling a mob phone overseas ?

I have been asked this when booking a flight :

Include your country code and access number in your mobile phone.

i.e. 63 + 918 + 9999999

I dont really know as i never use my mobile < xx

For my Australian mobile I write: +61 XXX XXX XXX or if it lets me: +61 (0) XXX XXX XXX
For my Chinese mobile I enter: +86 XX XXX XXX XXX

Where +61 and +86 are the country codes, the Xs are my phone number.
And in Australia, before the phone number for local dialling you would add a 0 (zero).

So presume for other countries similar formats...

Hope that helps - just my experience...