Membership expire problem?

Hello,

On my dating site, have Free membership: can not private message and Paid membership.
I restrict private message base on Membership.That is fine: Listing setup –>membership -> can read message

Problem is: When paid membership expired.Although, the time is expires ,however, user is still assigned in paid membership and he still send message !!

Is there any way to config when Paid membership expires, it will go to Free membership ?

Thanks you!