To cope with shyness you need to take a deep breath and do things slightly uncomfortable for you. Once you get used to that you can try things slightly more uncomfortable, until they also become ok. But you need to start and continue to get the benefit of change and self confidence, not to mention it becoming norm for you.
Go talk to someone you know who calls you, next time. You don't have to say much, just what you can, and which seems appropriate.
Start with your text friend maybe. That ought to not be too scary as they are a friend.