1. You can reach him at 010-9234-5678.

2. You can contact him at 010-9234-5678.
3. You can get in touch with him at 010-9234-5678.
4. You can call him him at 010-9234-5678.
5. You can dial him at 010-9234-5678.
(Are they all the same and grammatical? Which one is not grammatical?)

All are correct, but almost no one uses #5 anymore.