Do you have a citation for that? It’s a serious enough charge that it should never be made without one.
[1] https://www.documentcloud.org/documents/4106241-FCC-Calendar...
[2] https://www.americanoversight.org/watchdog-demands-details-o...
http://www.dslreports.com/shownews/ATT-Met-With-Ajit-Pai-in-...
"[F]lew to Barcelona to collect a bribe before passing this regulatory change" seems too strong a claim, but there should be serious questions after AT&T paid Cohen and also got a meeting that was off the record.
I don't imagine it actually changed Pai's opinion, but it seems unethical.