Don't tell them you're transferring to a competitor. That gives them all the excuses to 'save' your account.
My father was canceling his cable Internet service and reconnecting with another provider. I knew about all these tricks they use to retain customers. He had tried calling before and was put on hold, transferred, then spoke to someone for a few minutes and was again put on hold. He ended up hanging up the phone in frustration.
My solution to him was provide a different reason to cancel.
Told my father a better excuse. The next call lasted less than 1 minute. No transfers, no retention reps. A CSR cancelled the service. The reason: carpal tunnel syndrome. As soon as he said he can't use the keyboard/mouse anymore they immediately cancelled no other reason needed.
Hope this helps others!