I remember I had a phone a while back that I can save numbers like this
3197788876+9837
the phone will dial the first number:3197788876, when it connected, the phone will dial the next number automatically:9837

This is very useful when dialing international calls with IP card, where I need to put:
1, access number,
2, language (some cards),
3, the number you are trying to reach.

Use the letter 'p' (as in pause) in the telephone number string. For example 2015551212pp123 would pause for 2 seconds before entering extension 123 for an automated attendant.

Thanks, it works.
a note, in order to type 'p' during call mode, I need to press 'Fn + p'.