or
"Hello, I'm Xu Cheng. Please call me Cheng."
solves the problem either way.
Perhaps I would be talking to "Cheng", but later I would be talking about "Professor Cheng".
In my experience, while it is common for a Chinese personal name to be one syllable, it's not at all common for a person to be addressed by that one-syllable name. There are several strategies:
1. A person with a one-syllable name might be addressed by their whole name. For example, a 孙艺 might be called 孙艺 in speech, even though 孙 is the family name.
2. The person might have a nickname. For example, I know someone who goes by his nickname 哈哈; I've never heard his actual name.
3. The one-syllable name might be reduplicated; 袁璐 might be addressed as 璐璐.
4. The one-syllable name might be prefixed with 小; 李宁 might be addressed as 小宁.
Options 3 and 4 are diminutive constructions and may be too intimate for a strange man (or even a familiar man) to use to a woman.
Also reasonable:
"I am Doctor Xu."
"I'm Xu Cheng. I prefer my students to call me Doctor Xu."
"Hi, everybody calls me Frazz. Here's my card if you need to reach me."
"My name is something somethingElse, <whichever_is_family_name> is my family name, please call me <choice_to_be_called>"
Sometimes, I am not sure what is the proper way to introduce my Chinese name in English conversations? If I put family name at first, it would confuse English speakers. If I put given name first, the sound of my name feels so weird to me as that is not what I heard outside English environments.