I frequently change my C fare (or is it J now?) domestic tickets and I have never experienced this problem.
However, I have experienced the problem with claiming missing miles not working. I remember posting about this a few months ago when someone suggested I claim back the money for the flight if BA are so adamant that I did not travel the sector. Never tried it, but its an amusing thought.
Do you change it directly with BAEC or through a travel agent? (not sure if that makes any difference, but it sounds like an intelligent question
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