Checkout is listing ALL memberships instead of the one in the url..

Hi,

I am using a button on a sales page with the url of a specific membership id but the page is loading ALL available memberships instead of just the one membership.

For example:
https://mydomain.com/memberships/?membership_id=123 where 123 is a membership related to the sales page. Instead the specific membership in the url, the page is loading ALL available memberships.

Please can you tell me how to correct this as I do not want all memberships shown every time I add a button on a specifc membership/course sales page?

Many thanks
Jay.