Are these sentences the same?
I have to make a couple calls. and I have to make a couple of calls.

Question

Are these sentences the same?
I have to make a couple calls.  and I have to make a couple of calls.

Answer

The first one is wrong. It is always "couple of calls".

Answer

In spoken speech, they mean the same thing.  'Couple calls' is wrong, strictly speaking, but people often drop small words from sentences when speaking.

You also might hear it as "coupla calls" = "couple of calls"

You will only be corrected if you write it those ways, instead of "couple of".