How do I enter my alphabetical master partner ID on the Android keypad in mobile teamviewer?

 I set up a master partner ID on my desktop so that it remains the same between reboots.

It consists of a word.

It works fine works connecting remotely from a laptop. However trying to do a remote connect from my Android phone displays  an old style telephone pad with numbers and letters (eg 2 ABC and 3 DEF) to enter the partner ID. (see screenshot below)

However there is no way to access the letter part of the keypad. eg one key is labelled 2ABC but pressing it 3 times to get a 'B' simply gives me 3 lots of '2'.  There is no button to switch between numbers and letters.

 How do you enter an alphabetic partner id on Teamviewr mobile?

 (similar question was asked earleir by another user "Android keyboard will not allow letters when entering partner ID" but got no replies.