If you look around you can use either gprs, 3g or wlan on certain phones for yahoo,msn and all the other major messagner services. There are several free services such as hier and eqo for various platforms. There are also ones you can pay and then download such as im+.
I have just done a search and seen a im software called yehba which is free, but we have just started to look at how much Gprs-3g costs in phill as the
websites don't seem to tell us much.
On most of the brit networks you can pay a certain amount for data usage.
For example we use wlan in house which is of course free, and gprs outside which costs a set amount a month. Someone in phill can text or email my wife wherever she is.
Others i know get a blackberry account which can be used on some other phones (nokia smartphones for example) other than the blackberry type if you install the correct software. And send emails back and forth.
This can be useful when your a work in the uk and want to speak to loved ones in phill who are at home or the net cafe in the evening.