Absolutely yes! You can.
With TextApp, you can call any number in over 200 countries around the world, landline or mobile. Naturally, as a TextApp user, you can call your friends with the TextApp app installed.
The only difference between calling a TextApp friend or a regular number lies in the number. If you call a TextApp user on his/her number (starting with '+T 123'), it is free - no Credit balance required or deducted. If you call a regular number (a real call with country code), TextApp credits will be consumed.
Therefore, it’s a good idea to invite more friends to use TextApp, so that free calls can be expected.