Upvote:12
Expedia customer service hasn't been very helpful to you, but I would suggest you continue to call and email, asking for managers or higher ups. Generally staff will attempt to dismiss the issues, but when passed higher it is more likely to be sorted.
Phone: If you have previously called Expedia's customer services and your issue has not been resolved, you can call 0203 684 2910 about your problem. (worked in this case of overcharging)
Email: As @traveller mentioned in their comment you can email the CEO: ceoemail.com/s.php?id=ceo-10809, or you can also try [email protected] if you haven't already, this email has a 48 hour max response time and should give you an official complaint number etc.
Letter: Others have had success at the following address: Expedia Corporate Office Headquarters HQ, 3150 139th Ave. SE, Bellevue, WA 98005 USA
Personally, I always use social media such as twitter/facebook. Companies usually respond faster and resolve the issue properly when they are publicly called out. I've had issues resolved with Delta this way, but haven't tried Expedia specifically.
Hope you manage to solve this, but be warned that this is something that happens often with them, with some people taking them to small claims court.