There are a number of Mozilla related things you could have paid for. You can do donations to Mozilla and for Thunderbird and you can submit refunds if you want if this is the case of the charge. Mozilla has a number of subscription based products as in Mozilla VPN, MDN Plus and the premium/plus versions of Firefox Relay, Mozilla Monitor, Pocket. These are form links to sends tickets for help if you figure out what product you paid for. [https://support.mozilla.org/en-US/questions/new/firefox-private-network-vpn/form Mozilla VPN] [https://support.mozilla.org/en-US/questions/new/relay/form Firefox Relay] [https://support.mozilla.org/en-US/questions/new/monitor/form Mozilla Monitor] [https://support.mozilla.org/en-US/questions/new/pocket/form Pocket] [https://support.mozilla.org/en-US/questions/new/mdn-plus/form MDN Plus]