Then again, I used to be with Eon and their customer service is outrageously abysmal - dropped calls, 30+ minute hold times etc. With Ecotricity I get straight through to a local human every time.
The "supplier" for a consumer is actually basically just a bunch of legal contracts, a spreadsheet, a marketing budget and a call centre. And you do end up calling them when things go wrong with that part, which is too often. I usually end up talking to them at least once near the start of a relationship because they got something important wrong, and when I move home or any circumstances change.
It _should_ all be seamless but it often isn't. And ordinary consumers don't understand that it's just spreadsheets, they are genuinely distressed that a screw-up might mean their lights stop working, their food is ruined in the fridge etcetera. So this creates a reluctance to even risk using a different "supplier".
Right now it's super smooth for me, I went to full "smart meter" billing, there's a wireless box somewhere telling what it'll cost when I remember to look and the money vanishes from my current account on cue, no action needed for years at a time (need to review the tarif design, ie mix of fixed and variable charges online every few years or you get a shit default deal). But a decade ago I spent months contesting charges with one of these suppliers because they had a meter reference down wrong in some database and couldn't get the fix to "stick" so I'd get next door's usage billed, I'd complain, they'd "fix" it, same next month, repeat.