péngyou zhījiān jiào quánmíng hěn chángjiàn, dàn zài zhèngshì chǎnghé, xìng jiā zhíwèi gèng wěn

朋友之间叫全名很常见，但在正式场合，姓加职位更稳。

It's common to call friends by their full names, but in formal settings, using the surname plus title is safer.