You could say, "Sorry, I pocket dialed you. Please excuse the call."

"I butt dialed you" sounds more crude/impolite than "I pocket called you". "I dialed the wrong number" works in any situation

Sorry! Wrong number

If you didn't mean to make a call, but you made a call, you might say that you "butt dialed" someone. This comes from when you have your phone in your pocket, and your butt accidentally dials a phone number (or speed dial) you didn't intend to dial.

We usually refer to it as "a wrong number" and so we say "I accidentally dialled the wrong number" or "I accidentally got the wrong number" or just "Sorry! Wrong number! My mistake!"