Username change

I have had my current username/community profile 0263 for the whole time I have been a member of NAS, which is years now, and have been actively trying to get it changed for something more memorable – I am not very good with numbers. NAS staff whom I have been in touch with have attempted to get it changed for me but have not been able to do so. There seems to be an insurmountable problem which prevents any such change. Is it really as difficult as it seems?

I have given up hope of ever being able to change it, and I am fed up with trying. I am  so frustrated by it. I have thought about terminating my membership and re applying, which would most likely be the only way, but why should I have to do that? Is it really impossible change it?