Originally Posted by
Earthman
I can't transfer avios using combine my avios to BA either as I get an address/derails error even though the addresses and information are the same
It could be the phone number, it was for me until I corrected it. At BA it was +353 87 123 4567 and on EI it was 087 123 4567, so that caused the mismatch. Once I changed that, it worked seamlessly and continues to do so.
You should not get charged the offline booking fee if you point out you tried to do it online and it did not work.