comma after introductory clause [conjunction]: If anybody..., it

[Pidginboy]

If anybody calls me on phone it means I am no less popular.
If anybody calls me on phone, it means I am no less popular.

I am confused about use of comma in such context. Can I infer that long pauses require a comma?

 

[Joelline]

Not really. The general rule is that when a dependent clause begins a sentence, you should put a comma after it:
When he comes home, tell him that....
After he ate dinner, he ....
Because she was so old, she...
If you see Mary, tell her ....

By the way, we generally say, "on the phone."