I couldn't seem to get clarity from the NYT archive on this.
Here's my situation:
a former coworker who they play golf with and feel comfortable directly texting or calling anytime with questions
A century ago, it was standard to write any time as two words in all contexts. But it’s now perfectly acceptable to write anytime as one word when you’re using it as an adverb. However, some readers still consider it a casualism, so you may want to stick to the two-word version for extremely formal writing.