Cal here from Shopify, thanks for reaching out to us. How are you doing today?
Have you already added your card information to your store? Sometimes those emails are sent out when a trial expires, but if the card details are already added and there has been an invoice generated for a paid plan then a trial extension isn't possible.
I'd be happy to take a look at your account to confirm this, however! Could you share your MyShopify URL with me and I'll take a look? Thanks!
Thanks, I have emailed the account owner requesting a little more information on this particular case.