I cannot usually tell at the start of the call if they will be helpful or not. But as soon as they ask questions, it's easy to figure out their skill level. IME with BoA, there are people in the US who barely understood my request and asked all the wrong things and I knew I had to hang up on them. Folks at chase and amex were far better. The amex folks were in India I think. You can also tell that some CSRs are used to talking to people with comprehension difficulties or people who couldn't be bothered to engage in any courtesies and that may be one of the reasons for their approach.

call center jobs are not very desirable jobs so even in 3rd world countries you generally get people with below average talent. The cream of the crop eventually makes it to silicon valley and you can see what people with accents have done here. I don't know of anyone who chooses to do a customer service job. It's a necessity not a choice so I don't expect to get great service out of them. I"m delighted when I get someone who does. Last time I booked a complex itinerary with UA in 9 minutes (including payment), that's how skilled this lady was.

I don't have a lot of CSR time like Lucky so I may be wrong but that's just my 2 cents.