I've tried Googling this but the answers only relate to smartphones, not the type that just do calls and texts and not a huge amount besides. Has anyone come across mobiles with almost no storage capacity for sms messages? What do you do about it? The phone itself should be able to store 500. I would have taken it back but my relative, whose phone it is, hasn't done so.
I know someone who had a similar issue on an old very basic Nokia phone (possibly a 301?). I think the onboard storage was something like 2Mb, and she was always running out of space for messages. I seem to recall that the phone did take a Micro SD memory card, which was supposed to expand the memory, but I don't think she ever found out how to transfer the text messages storage from the phone memory to the SD card, and has since lost the phone.
Sorry if that's a bit vague and unhelpful, but it might just give you something to go on.
By the way, I need to correct myself. I'm not entirely sure which Nokia my relative has. One basic Nokia should hold 500 sms messages, but you can't expand the memory, but you can with a slightly more expensive model.
So I think I'd need to find out exactly which is in question and work from there. Or not.