I am available to talk on the phone.
I am open to talk on the phone.
Do they have the same meaning in conversation or any scheduled meeting?
A: When will you be available to talk?
Can we reply with "I am open at 4:00 PM"? in a telephonic business context?
kumenglishI am available to talk on the phone.
OK.
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kumenglishI am open to talking on the phone.
See above, but that means something else. It means that you are willing to consider something. See entry #7.1 for "open" as an adjective in the link below.
....lexico.com/definition/open
kumenglishWhen will you be available to talk?Can we reply with "I am open at 4:00 PM"?
No, see above.
Comments
I would tell this when the person wants to how he or she can communicate with/contact me.
This I would say when I sense that the person is not sure if I am comfortable discussing the matter on the phone.
I haven't heard anyone saying that. (But, I am not native speaker)