Dreaming that you try to dial the phone but can't, or that you keep making dialing mistakes and can't make the connection, could mean:
You're feeling frustrated in communicating something (a message, a need, etc.)
You're isolated or cut off from others
You feel the need to reach out or ask for help
Your subconscious mind is imagining a worst-case scenario based on a fear of needing help and not being able to get it
Trouble dialing a phone can also mean you're having a Toxic Dream.