A booty call relationship is a casual sexual relationship: you call/text them (or they call/text you) whenever you feel like having sex, you meet and hook up. That's all, no strings attached. It is like a friends with benefits relationship, but without the “friends” part. What to do if you don't feel like having casual sex with your booty call anymore? How to end a booty call relationship?
This kind of relationship has virtually zero level of commitment. You don't owe each other anything. However, it doesn't mean that you can simply disappear from their life when you are tired of hooking up. Cutting people off like that is just plain rude. You surely are a nice person, so you will have to find a way to end things amicably.
There is a whole bunch of reasons for ending a booty call relationship. You may grow tired of having casual sex. You may find someone you want to be in a romantic relationship with. You may start falling for your booty call (and that's usually a terrible, terrible scenario). You need to find your reason to be sure you want to end this relationship.
Then meet them in a public place and simply tell you don't want to hook up anymore. Be honest, but firm. Say that things are not working out for you anymore. You can leave it at that because a booty call relationship is not the kind of relationship where explicit communication is always necessary. You are not obligated to explain anything. But you can if you feel like you need to and if they want to hear your explanation.
It is very important to resist the temptation to have sex one last time. That is why you need to meet in a public place and cut your conversation short. One last time turns into two, and soon you find yourself making one booty call after another. When you stop having sex, you stop. When it's over, its over.
The best thing you can do is go cold turkey. After having the “we need to break things off” conversation, stop seeing them, stop talking to them, stop texting them. It can be hard if you go to the same college or have mutual friends, but you absolutely must keep communication to a minimum. Hanging out together or flirting via text will inevitably lead to another hook up, and you don't want this, do you? When you go out with friends, ask someone to keep you from drunk-texting, just in case.
One more thing. Breaking up with someone you've been dating by a text message or e-mail is a major faux pas, but ending a booty call relationship this way can be totally OK. So if you don't feel like meeting them, you can call or send a text, they are not likely to get offended. However, there is no need to be rude or mean, because your paths might cross again under different circumstances.