Re booking: U63SN4 From LHR to GCM and return. Initial booking for 19th May. Unfortunately our PCR Covid - 19 tests were not completed in time before departure. Living on the Isle of Wight makes this procedure more difficult because of the need to send the tests to a mainland laboratory. Our only option was to postpone our journey. We contacted BA to re-book for 2nd June and were charged an additional £3732.58 plus £1 for re-reserving our seats in Club World. This charge is totally contrary to BA's advertising about how flexible the airline is and it makes great play about the 'Booking with Confidence' commitment. Meanwhile, BA cancelled our return flight TWICE meaning we had to re-arrange all our plans and documentation TWICE. Seems that BA can change flights when it wants to but for us it's a costly and stressful pastime. We've been flying this route for many years and consider ourselves loyal BA customers but the treatment we have just experienced has certainly tainted our opinion of BA and doubt if it can maintain being the 'World's Favourite Airline' for very much longer. We have also written to the Chairman and CEO, Mr Sean L Doyle.