I've been a 2 Degrees mobile customer for 13 years: I've been a broadband customer for a few years less (just after 2 Degree acquired the ISP). As I'm moving overseas I need to cancel both services. Here's how it's gone:

 

1. Broadband team: explain, give the date of disconnection, sent a bag for the hardware return. And then received a series of email reminders about the hardware return with weeks left in the service. An email to their team seems to have stopped this.
2. Mobile team: Attempt #1 - you have to call within the billing period, but there's no advance notice requirement, so you can at any time within that last billing period. Attempt #2 - no you can't give notice 25 days in advance, you can only call the day you want it disconnected....at which point I got firm, your man put me on hold, and apologised and accepted my request.

So #1 is like what seemed like an amicable breakup, but the other party's adding a lot of drama that ain't helpful. #2 was maddening because my husband was able to cancel his three weeks in advance, no problem

New ISP (in Ireland) with 2G fibre is already booked for an install. Complete with free Wifi 7 router.