Someone has used my paypal account to pay for Facebook ads

I logged into my online bank account and saw that over the past week or so, payments (totalling over £200) were paid to Facebook Ads via my paypal account. I have not bought any ads on Facebook since 2015, but this meant my paypal account approved payments to Facebook. My immediate thought was that my Facebook had been hacked again (it was hacked a month ago, but I changed all my passwords to everything ) - so I checked to see if a hacker had bought ads using my account - They hadn't! - no ads had been purchased through my account - So someone, with a different account had bought ads using my paypal account - What can be done about this - I've reported it to Facebook, but I've heard nothing back from them - I've taken out paypal disputes for all the payments made - I've cancelled my debit card which was registered with paypal (and from which the payments from my bank had been taken) - is there any chance I'll get my money back? Has this happened to anyone else?