I checked your account and your subscription has been active for some time now. You can make group video call and since you also have Unlimited US&Canada you can call phone numbers in these 2 countries.
When I checked your call history then I noticed that you have tried to call outside of US and Canada. Here is your call history: https://secure.skype.com/account/call-history
Important: Make sure you dial the number with correct country code +1 (for US)
Your subscriptions: https://secure.skype.com/account/call-phones/packa
Regarding customer service, currently Skype is not able to offer phone support for more than half a billion users, but Skype has email and chat support.
Since most questions are answered in FAQ's it will be offered as first option, but if you can't find an answer from FAQ's then simply search with keywords customer support or just support and first link you find is: https://support.skype.com/faq/FA1170
Rather than sending email to one specific address it's much more efficient to fill out support form, based on which your case will be sent to specialized department right away.
Since you have Skype Premium you have access to chat support:
I know it might seem like Skype is hiding, but I can assure you it's actually the opposite. Millions of customers every single day find their answer from FAQ's, which leaves enough resources for customer service to focus on cases that cannot be solved with FAQ's.
If answer was helpful please mark it with Kudos and if issue is resolved mark it with solution. This will help other users find this answer more easily. Thanks in advance!