A very sensible decision.
I did similar, but as I never in the last decade used the landline phone for outgoing calls, and only four (now three) people ever called in legitimately on it, didn't bother paying for VOIP.
Since then I've decided to install security cameras, and consider in-building recording equipment pointless as that would walk with whatever else was taken, I've also bought the Three Huawei-B311 + SIM and I'm still quids in, like you. I (luckily) have unlimited cloud storage effectively free from 1 & 1 so my cameras upload frequently via that router. (That 1 & 1 deal seems to have vanished following their takeover by IONOS).
4G really is a viable alternative for less bandwith-demanding households. (Possibly code for zero-teenager presence households). Though I fear the idea is catching on, as today for the first time I had buffering problems with the FI Mexican GP.
Dammit! I tried to correct that by turning on the "Hotspot" of my phone, which helped a bit, but just now realised both the race-streaming laptop running NowTV and the Live F1 timing on my iPad switched to it, when I meant to split them. I doubt if that made much difference.
I did of course need at that time to move my phone from EE to Three, and EE is the better, but Three has not caused me problems since then except for the recent cock-up. EE can suffer from cock-ups too.
My broadband basic info/help site -
www.robertos.me.uk. Domains, site and mail hosting -
Tsohost.
Connection - Three 4G, tbb tests normally 35-45Mpbs down, 65Mbps off-peak, 9-24 up.
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"Democracy means simply the bludgeoning of the people by the people for the people." Oscar Wilde