There's nothing unusual about airline schedules changing. I'm afraid it is a hazard of booking six months or so in advance. I've have connections screwed up by schedule change before - UA and JJ leap to mind as culprits but I'm sure it can happen with most airlines.

BA customer service lines can be pretty horrible for non-status pax - something which I suspect most people who post on here don't know anything about. But then expedia ought to be able to sort it out - but their telephone service is terrible too, so much so that I avoid using them now.

There are some travel agencies which have genuinely good telephone service for pax without any special status experiencing problems. Tablet Hotels leaps to mind. But that doesn't help the OP.