I'm glad we have options here in Europe. Not many, but there are at least 3 mobile and internet providers at my location, so whenever one tries to pull something like this, I just call them that I'm switching providers. I've netted a permanent 50% discount and even managed to convince them to keep the discount at my old flat (which was a student's shared flat where my friends still live) and also transfer it to my new home I have with my partner.

As far as I know, they can give you massive discounts, but you have to be willing to go through hell and run into a good call operator.

But also, that was like 10 years ago and I didn't need to do it again. I can imagine that in the age of clankers, things may be a lot different (also with the transition to late-stage capitalism and enshittification).