I once had a traffic controller give me a hard time about how I requested IFR clearance once in the air. I had previously filed an IFR flight plan, and took off from my untowered home airport. On approach control's frequency, I said:
Tampa Approach, Cirrus 123AB, 5 miles southeast of Tampa Exec at 1000 feet, IFR to Ft. Lauderdale Exec
The approach controller responded, annoyed, saying something like "Well do you have an IFR flight plan or are you reporting IFR??"
I had always used that phraseology because it seems the least wordy way to get the info across, which can be helpful when the freq is busy. What is the technically correct way to get an IFR clearance on an existing IFR flight plan?