Calling and texting over the border?

I live in NI, frequently need to call landlines in Donegal and send texts, to companies and businesses, and I’ve not found a solution for this that isn’t really expensive or awkward. They don’t use WhatsApp. E sims I find to be really unreliable (no one knows why, including the e sim companies) and I’ve been using spusu but they don’t work for texts over the border (they also don’t know why, lots of helpline calls and SIM card replacements but nothing sorted out there).

Anyone else cracked this?