How to change display number of A number on cucm 10.5

[anuwat_n@mfec.co.th]

I want to change A number when i call to PSTN in cucm 10.5

e.g. I use extension number 2951 (external phone number mask is 02029xxxx ) call to moblie phone but i want to dispaly  A number on mobile is 0333xxxx 

How i can do it ?

[piyush aghera]

Do you want to change display number to 0333xxxx for just one extension or for all the extensions ?

[anuwat_n@mfec.co.th]

only one extension

[piyush aghera]

In that case, your best bet would be to change External Phone Number Mask on DN.   I am assuming that you do not have any Calling Party Transform Mask on your Route Patterns.