Sophia here from Shopify. I'm unable to call you, but I can help you get in touch with our Support team via callback if a phone call is your preferred method of contact. Live chat and email support are also available 24/7 even if you're not logged in on the Shopify Help Center (you can select "Continue without logging in" to find the contact options available in your area). Response times have been delayed as we're experiencing such a high volume of requests at this time, but our team is working hard to respond as quickly as possible.
It sounds like you haven't been able to login to your admin, is that correct? If there's an error message appearing when you attempt to login to Shopify, please let me know and share a screenshot here if you can. As for the issue with the shipping cost on eBay, please note that the eBay sales channel is supported by a specialized team outside of Shopify. I recommend checking out the eBay sales channel quick start guide first, then contacting eBay sales channel support at email@example.com or by phone at 1 (855) 411-3376 if you're unable to find what you're looking for in the guide.