Not gonna lie, I've generally had amazing customer service.
One thing to remember is that these people are just enforcing policies handed down to them. When they say, "No, you can't keep your old data plan and get a new subsidized phone" they aren't being dicks, just stating a fact.
I just tried to sneak in a Note2 in and thought I got very lucky.
The Pre-Order website was messed up, and allowed me to check out while having "keep existing $29.99 plan" option checked.
When I got my order receipt, it clearly said "with 2Gb plan".
When I called CS, they said that it was obviously an error that they couldn't recreate, and I cancelled my order to avoid getting screwed out of my data plan.
I wasn't mad at the lady, it wasn't her fault, but it sucked all the same.