Transferring my payment to another SIM

Hi, newby but tricky question!

I've had a SMARTY SIM for a few years in a portable router which is lost (I know, I know, I should've cancelled my SMARTY plan ages ago!).

I help run a tech drop-in for older people (even older than me) and the router we use has a SMARTY SIM which was provided by a local charity.

Their SIM stopped working a couple of weeks ago, so I'm assuming someone at the charity has decided they can no longer afford to keep it running.

Is it possible for me to pay for the 'charity' SIM instead of paying for my own?

Unsurprisingly, I couldn't find anything in the help files for this, nor could I find any way of contacting SMARTY direct.

If it's there, apologies. I blame the heat...

TIA

Patrick