Stop in for a cup of coffee

AT&T told me that they couldn't maintain the speed because I was at the "end of the line"... Everybody upstream was sucking up the bandwidth...

Not my fault that I was sucking the hind tit... I like cable internet much better... I think that they offer a 100 Mbps package now for a nice price, they sent me a letter telling me that I can upgrade, but I haven't followed through yet... I wanted to catch up on a few bills first and now want to let them get the new line run... I'm on an 8 --- whatever line right now and they are going to run a 11 --- line when they come to bury the new one soon...
Tim might know more.
I think you got a AT&T lackey reading from a script. DSL sends packets on the same wires the analog current carrying voice. The final leg from the exchange should not be shared - it just might be long, old, and oxidized or have bad connections.
Cable service does share the line - almost to the house. If it makes you feel better, everyone suffers when there is high demand. That's one of the complaints with cable here. They need to go to those better lines, whatever they are, if they're planning to be competitive against FIOS and soon or later, 5G.