REFUND & DOUBLE CHARGED--HELP!!

My father just noticed on his bank account that he was charged for Avast TWICE in February & the computer we had installed it to a couple years ago died & he’s changed email addresses from the one used for Avast login info so we have no idea how to get login info, order # or anything. Need to know how to get his login info, order # & info abt how to obtain refund for the two charges in February AND to stop from being charged ever again.

https://www.avast.com/faq.php?article=AVKB24#artTitle (Orders and Renewals)