When I send text messages to people some of them say they cannot read the message and get one of 2 notes on the phones.
The recipients phone either says "null" or Unsupported message format.

If I sent texts to a BB it works fine and the last one I sent to an iphone also worked.

The phones that gave problems that I know of were a Samsung and a Nokia.

I was advised by my service provider to wipe my phone which I did but that has not helped

Please can someone advise how I can fix this probem

Hi

Try and change the data Coding undert he options , mine working fine now with 7bit.