Telephonically.
Found in a job posting at a prominent medical devices company website. Yet dictionary.com has a listing for it (well, for telephonical, and with the adverb form listed afterword with no definition itself.)
Who knew?
Hmm. I knew. My little sister told me about a group of some sort that had “telephonic” in its name by, at latest, 1979, and probably earlier. She used the word “telephonically” at that time.
The M-W Collegiate, 11th ed., has it dating from 1840!
Thefreedictionary.com, Firefox’s extension, has it:
Telephon´ically
adv. 1. By telephonic means or processes; by the use of the telephone.
Are you in denial of “telephony”, too?
If you are, the phrase “IP telephony” will seem like some impossible urological event.
I use “telephonic” all the time – as in “I’ll be in telephonic,” which is short for “telephonic communication with you soon.”
Seriously.
Of course, I’m a Doper, thus weird, QED.
Alexander Haig famously used the term, during, I believe, the Iran-Contra hearings. That was the first use I’d ever heard of the word, and I recall much was made of his use of the term.