I am coming to the end of a DONE4 - both in terms of flights and ticket validity (which expires on 22 July 2015). Ticket was issued by BA.

I was unable to fly HKG-DPS-HKG last week due to DPS being closed as a result of volcanic ash. CX announced that they would reissue all tickets provided travel was before 15 Sept 2015.

Before making final flight to LHR on 22 July I am scheduled to fly HKG-CMB-HKG for a few days departing tomorrow.

CX have refused to reissue the HKG-DPS-HKG coupon for travel in early September unless BA extends the validity of the DONE4 beyond the dates of travel in September.

BA say they cannot extend validity of DONE4 and that my beef lies with CX.

BA also indicate that if I was to get stranded in beyond DPS if volcano causes more problems, then I could lose all remaining flights on DONE4 if I do not travel before validity expires.

Question: Can BA extend the validity of a DONEX at its discretion?