Can I say "due call"?

If the phone call has not been made by the expected time, I would recommend using "overdue" instead. For example: "I need to make an overdue call." or "The phone call is overdue."

"The phone call is due tomorrow" can be used to indicate an expected time in the future or "The phone call was due yesterday" for a missed call. I cannot think of a situation where I would use the phrase "due call" to refer to a call that was not made at the expected time.

If you mean a call that was planned, then you can say "a due call", in the same way you say "talks are due to adjourn tomorrow".

If you forgot, then I assume there was a predetermined time you were supposed to call. In that case, "past due call" would be more applicable, and I think perfectly acceptable.

Due could take on different meanings depending on whether it is placed before or after the noun it modifies. Ordinarily, due would mean necessary; appropriate; required (not with respect to time) when placed before a noun, as in due attention, due diligence, due regard, etc. In this case, however, due should follow the noun if it is to acquire it's more popular meaning of required at a certain time; owed; etc.

Options in this case are:

• A call I forgot to make
• A call I am yet to make
• A call I [still] have to make
• A call I need to make
• An overdue call
• A long overdue call
• A call [long] overdue
• A call due [when e.g. yesterday]
• A call past due

I should also add that due call would usually be taken to mean a required call (not of the telephone variety, more often than not), as in the following example:

First speaker: 'I wish Joe hadn't called the superintendent out on that issue.'

Second speaker: 'I disagree! The superintendent was clearly in the wrong.'

Third speaker: 'Yeah, that was definitely a due call.'