I use the phase "no problem" in my work every day. I fix peoples computers. They might say to me "oh yah, could you also look at my anti virus, I don't think it's working". I reply with "no problem". What I am saying (and I believe, what they are hearing) is I will take care of it. I have used that phase thousands of times over the past 13 years to my clients and not one time has one of them not understood what I meant, or had a problem with it, not sure how come you do?
I gotta say I can understand why others might call you out on this and I am not trying to start anything, but man you sound like a jerk. If I was a serving your table, it would be my last day at that job, cause I wouldn't take your ****. Just sayin.