how to use 3 different accounts and receive messages on facebook messenger on iphone?

I have to manage 3 facebook accounts on my cell phone, and I need to have access to them on my iphone, only the messenger needs to be available, only the applications that I tested, nothing works perfect, on android I can duplicate the messenger application and that's how I get it access the 3 messenger, on the iphone how could I do that without giving me a headache?