Unauthorized PayPal charges from Skype Communications Sarl

Skype/Microsoft does not bill people randomly. If you were charged, you or someone with access to your account purchased Skype credit, a subscription, or have a renewing ~$100+ subscription with autopay enabled. A purchase made on any account is a normal transaction and would not be considered weird. However, the amount of purchases that can be made in a short period of time is purposefully limited.

If you chose to abandon an account, it is wise to close it or at least remove payment information and cancel any subscriptions (if you had any). Since you have PayPal linked to that account you should immediately terminate any agreements you have between PayPal and Skype/Microsoft so that transactions do not immediately go through without additional verification. This is performed on PayPal's site [paypal.com]. You may want to verify the security options of your PayPal account to ensure it has not been breached. It may also be wise to scan your computers for malware (and remove any found) to ensure your computers/devices are not broadcasting your personal account information and passwords.

Your Skype emails will tell you exactly which account these charges are from. You need to sign in to that account. If you do not have access to it, regain access and remove any unknown email addresses or verification methods. You can then choose to lock down your account with more verifications options or close it.

If you cannot immediately regain access, it would be wise to contact PayPal and/or your payment provider to contest the transactions as fraudulent. They will likely still encourage to properly cancel the purchases and terminate any agreements to avoid future charges.

You can contact Skype customer support over live chat. However, they can only provide limited support if you are unable to sign in to the account in which the charges are present.