Suggestions in dealing with problem members?

I have two sisters who are both previous members who I was hoping I'd never see again. One slept with half the guys in the gym and created all kinds of drama and the other skipped out on $110 bill for her and her fiancee in 2015. Fast forward to a week ago, they call to inquire our prices to come back - my manager quotes pro-rated month and $39 new member fee each. They complain, my manager tells them about our great classes and awesome gym and they hang up and manage to sign up for two fit passes. I email support@liftbrands and ask them to cancel the passes and refund their money. Fitware responds with no problem. When I see the customers I nicely explain that they aren't eligible for trials as previous members. The attitude begins... The sisters think that since they got away with signing up they should each get a month for $8.95. Silly me, I actually thought corporate would support their Franchisee in this rare request. Without actually knowing what was said between Fitware support, legal... the sisters come in a couple days later as guests from another Snap feeling pretty smug. Without writing a diatribe, they say Corporate suggested they sign up at another club and keep using mine. I was pretty surprised all the way around. Then they filed the first complaint against me with HQ I've ever had. 

I think I have a simple solution, I've never accepted any money from these customers, don't I "reserve the right to refuse service to anyone"? I don't feel comfortable with these customers in my gym for many reasons. Do I file a restraining order against them? I have a good relationship with the club they signed up with and the local PD. I'm pretty sure they'll make the sisters club only for me. I've only kicked out 2 people - both guys - and it's never been a problem with them returning. These two are treating me like I owe them child support - I don't think they have any rights here whatsoever. 

Any thoughts for me zees?