Originally Posted by
ThatT1Feeling
Hi Charlyonge, and welcome to the forum!
I have called BA before to request extensions to various things. My experience has been that BA can extend the vouchers which they control (Gold Upgrade Vouchers etc.), but they can't extend Amex vouchers.
I would recommend you try Amex first as they are the ones who issue the voucher you need extending.
BA have extended by Amex voucher before, via the-then BA rep on here. But this was a few years ago when they had some level of customer service.