You should never have a reason to call IB's customer service. Period. Everything can be dealt with via email and the website. I had to send them an email the other day because a trade did not show up on my daily statement. They got back to me in 1 hour with an updated daily statement. End of problem. I deal with routine stuff like this all the time via email and have never gotten an unsatisfactory or untimely response.
There was one time, when I first started trading with IB, that I was 4x and they closed a trade down on me at 3:50 right before a significant move in my direction. I sent them an email and asked for a rebate on the commission only, they said no, I said I was going to close my account, and they told me how to close it.
That's about as bad as I have had it, but I really wasn't all that mad in the first place, just bustin' balls and they called me on it.