We live in Eastern Europe, and when we first came here (about 12 years ago, the service provide by the (state) ISP was lousy – very very slow, and prone to fail frequently – Friday evening was always a good time, then it would come back on Monday morning when the local engineer(?) came back on duty.
Eventually we got a mobile phone, but at that time, it could not be used as a hotspot, although later it was possible. About 5 years ago, by chance, we became friendly with the girl in the local mobile providers shop – she spoke good English, which helped. She mentioned that they could provide up to 50 GBytes/month of broadband data connection free using a fixed router using the SIM fitted in the mobile phones, but many of her customers had complained that it didn't work, and had returned their routers – she had a big pile of them. I asked if I could try one, so she gave me half-a dozen to test after she talked to her manager.
I took them home, plugged in my SIM, and sure enough, it didn't work – then after a bit of checking, I found out that the SIM was retained in its socket by a metal strap – you had to slide the SIM under the strap – but it was so very easy to slide it in so it went over the strap (and very difficult to actually see) – so no connection. All the routers I had been loaned worked when I made sure that the SIM was correctly installed, and eventually I found about 3 truly dud routers from around 50. I got a free SIM for a year as a result as a thankyou from the manager.
Three months ago, the mobile provider (it also provides service in Western Europe and the UK), bought out the state Telecom concern, and now operates that as well – and its service is vastly better than it used to be.
I have no idea what the moral of this story is (was), but it worked for me.