我叫 Roy 我姓 Jones 我是 a famous boxer.

我叫：It must be followed by a name. 我姓：It must be followed by your Surname. 我是Can be followed by a name，it means that who are you.just like “i am Issac.” Career can also be followed.To express one's work. My English is not very good. I hope I can help you.૧(●´৺`●)૭

谢谢。 Thank you for the help!

just different verb, 叫 to ask name 姓 for surname 是 are,am,is,can be your name,profession,Chinese... for example: Donald Trump--- 他叫Donald or Donald Trump 他姓Trump 他是美国人（American）他是总统（president）他是有钱人（rich person）他是老板（boss）.... you can practice with “Kim Kardashian” ‘Justin Bieber’ :)

我叫 X I am called X 我姓 X My last name is X 我是 X I am X Same nunances as in English.