Left BT TV/internet last week having been a customer for about 15 years. Phoned them to see if I could get a better deal but they weren't interested in the slightest so switched to Sky.
Almost from the minute the switch was confirmed I have been getting calls from their retentions team about 4-5 times a day. They never leave a message but the one time I picked up to tell them to sod off, the line cut immediately.
If they couldn't be arsed to keep me as a customer and then made me go through the hassle of switching, I'm not sure what makes them think I'm going to waste hours of my life switching back again.