I've made a booking using a companion voucher this morning and want to change the return date (because I'm an idiot and got it wrong).

My understanding was that I could change it within 24 hours of making the booking without incurring a change fee, but I can't seem to do that online - I'm told I have to pay £70.

I've tried ringing BA and the phone gets cut off every time I get to the end of selecting the options - I get a ringtone for a while and then it goes quiet, and then cuts off. I've tried four times now, using different phones, so it's not me.

Update: I wasn't able to cancel the flight online, as it's a Gatwick flight. I got through to BA on my fifth attempt of phoning (having given up on the website and twitter bots) and was able to cancel for free. There is a change fee by phone as well as online even if done within 24 hours of booking, so cancelling makes more sense. Fingers crossed I can rebook.