paste command appears in the three dot menu after you have copied a number. 'Paste' will be the first command (top).
Aaaand indeed, if I copy only a "number" then it's there, and I can use it.

Thank you guys for the help.
But, actually this is more complicated than this, I tried to reproduce the situation and it seems that even with very long texts TruePhone manages to paste it and convert it into numbers, but there are certain patterns (mostly lots of text with some numbers between) when the Paste command is not displayed.
I copied a whole SMS (SMS Messenger by Simple Mobile Tools does not support copying part of a message, doh), and I thought I will paste it and clean it up afterwards.
Nevertheless I would like to suggest a smaller and a bigger feature/change.
1. Always show the Paste command and if it is inapplicable to the current clipboard content then show it greyed out. This way the user knows that the feature is there but it is currently unavailable for some reason.
2. Add an option to decide how should a mixed (letters, numbers) clipboard content be handled:
- use it as it works currently by representing the letters with numbers: really nice for those funny phone numbers written with letters (Phonewords?!)
- use only the numbers (and filter out any letters): useful for situations when a bigger text contains a number the user would like to call.
Maybe instead of the option, there should be two Paste commands depending on the content of the clipboard.