Arik Air does not appear in the airline list.
Meridiana shows correctly in the airplane list but the callsign should be changed to Meridiana from Merair (Pfac731 group). Also, I found the .wav files for Air Libya (Pfac217 group) however the airline name does not appear in the list.
Meridiana had the callsign "Merair" in the past, and this is recorded in the wav files.
Since this airline ceased operation, one could argue that both callsigns could be valid, depending on the historical time you are simulating.
If you want to show "Meridiana", you can edit PF3/captions.ini (make a copy of the original and modified file, so you know what to change after PF3 updates), but if you want to hear "Meridiana" you would need to edit more than 100 .wav files (e.g. using pfac972 "Trans Meridian", cut the Trans, append an "a" from somewhere else), which is probably more work than it is worth.
Arik Air would need new .wav files, but you could search for a similar sounding one (A. K. Air? Ank Air?) and just change the text in captions.ini.
You can find "Tibesti Air Libya" (seems to be the old name) in the drop down list. Feel free to change it in PF3/Data/pf3_callsigns.dat (make copies as mentioned above).
Dave, maybe you can change this one?