The A13 is a VoLTE certified therefore should work did you followed this guide https://fizz.ca/en/faq/how-do-i-set-up-call-forwarding
Can you try the sim in a different phone?
Do you have unlimited calls or an addon for calls or money in your wallet?
If nothing helps please contact the support
You can chat in direct
• Sign into your account
• Follow the link on this page: https://fizz.ca/en/faq/im-unable-log-my-fizz-account-what-do-i-do
• Wait 3 seconds for the green bubble with a '❔' appears at the bottom right of the browser, if you use a phone you must use it in desktop or horizontal mode
• Choose the option ? chat
• If the green bubble does not appear make sure your ad blocker is disabled, otherwise try with another browser.
Or by private message on Facebook: https://www.facebook.com/fizzca/