I have no experience with D4 and it's probably not your issue but I know that 3 cards do not work with old phones as 3 is only 3/4/5G and 3G only works on 2100Mhz, not 900MHz and no 2G at all.
GiffGaff that runs on O2 network on the other hand has worked in anything I could throw at it including factory handset in my old 1997 S8. If you are not using it much you just fill it up with credit instead of GoodyBags and it lasts forever, I have had it for several years just as a backup and still have £9.66 left from the £10 initial topup. Obviously it would drain much more quickly if using it for data daily as it is 5p/MB.
Another option could be
https://www.1pmobile.com/ that runs on EE network 1p/MB which does 2G but only 2100MHz 3G, not 900MHz 3G or if car uses more data you can get Vodafone Basic 8GB
https://www.vodafone.co.uk/shop/bund...2e8c007648afor £10 per month which works 2G and 900/2100MHz 3G. If you are lucky enough to have newer modem in phone module it should work on 4G as well but considering it does not work on 3, it's probably older 3G modem