When making a call sometimes there won't be no rining sound, the other person cant hear me and I cant hear them. The only thing I can do to fix it is to turn the phone off and then back on again. This happens at random times throughout the week. Any help?

I also get the no sim card inserted message aswell.

Sims get old and wear out. You may have a hardware problem. I always get a sound when I call.

thanks for that i'll try and get a new sim and see how it goes. If the problem still occured would I be able to send it back to Nokia as part of the warranty?

Thanks

Yes, no sound on a phone would definitely be covered. But also try re-flashing it before you give up, see http://wiki.maemo.org/Updating_the_firmware