Multi-Carrier SIM for Business

Afternoon all.  Does anyone have any experince of using Multi-Carrier SIMS?  Our current EE (business) contract is about to run out, they've been frankly aweful, especially the roaming aspect requiring us to (sh1z you not) send a text to change the contract over, so that we can roam without getting stung for massive charges, then do the same on return.  EE has also been really patchy for anumber of people in doors, and Wifi calling, not always working well.  So open to suggestions.  Only about a 8 phones.  ta.