I realize it's hard to endure; it's happened to me also. I actually have very good hearing, and I still struggle at times to understand people in c/s who don't have English as their primary language.
What I have had to learn to do is treat them nice and ask for someone else. I've literally said to a few of them "I'm sorry, I just can't understand you well enough for me to feel comfortable conducting business. I don't mean to be rude, but can you pass my call on up to your supervisor, please?" If you say that in a nice tone of voice, it typically gets passed on quickly. Yes, it's a PITB to have to do this. It might even take more than one step upwards; perhaps multiple requests.
Again, we have to realize that the process (the customer service experience) is a function of several things and that person on the other end of the phone is only a small spoke in a big wheel. Treat the other person on the phone as you'd want to be treated, and push your anger towards the company. It's OK to do a follow-up call and log a complaint about the c/s reps effect. Just do it politely. If you don't complain, nothing will get changed for the better.
And to be accurate, I've had some really crappy customer service experiences right here in the good ol' USA. The problems are not unique to foreign call centers. I've had folks right here at home make life miserable. I may understand them better, but the service was just as crappy, and sometimes worse.