As you say on the post , i think you need to edit the Title of the post by changing 1 year to 2 months guarantee.
The subscription may work for 1 year. I guarantee 2 months
I would recommend that you remove the "1 year" out of your title, and just indicate in your top post that while these accounts may be valid for 1 year, that you can only guarantee 2 months of the service.
However, I have a question. If my subscription expires
after those 2 months with the guarantee, will you have new subscriptions available for sale? Or are all of the subscriptions you're selling based on the same admin account?