When work gave me a free phone, I paid a one time fee of $20 to transfer my service to google voice. Google voice lets you text or call anyone for free from any computer, tablet, or phone for free (so if you didn't want to pay $20 to use your old phone number you could just get a free google number). Plus you can have google voice forward calls from a cellphone to your home phone, etc.
No reason to pay per text message... I'd go broke in half a day!
Nice tip, I've been looking for something to replace Yahoo messenger which went in the tank.