How do I make another Icloud account when it says I've reached the maximum number of accounts?

I forgot my past accounts and can't make a new one. I didn't know you could only have 3 accounts. 1 was already on it from the person I bought the phone from, and the other two I forgot. How do I fix it to where I can make a new account? I really need to know because I happen to lose my phone often and the "Find My Phone" thing was really useful when I had my other accounts. Please help.