We call that a 'pocket dial' in English, so you could say "Sorry, I pocket dialed you!". But you could say either 'by accident' or 'by mistake' in this case and either would sound totally natural and correct. "I called you by accident" or "I called you by mistake"...they mean the same thing.

Hello, in American English, very informally, we also use the expression "Sorry, I (must have, think I, bet I) butt-dialed you. Butt-dialing refers to the pressure applied to a phone in one's back pocket when she sits down that sometimes inadvertently causes a number to be dialed.

Hello, in American English, very informally, we also use the expression "Sorry, I (must have, think I, bet I) butt-dialed you. Butt-dialing refers to the pressure applied to a phone in one's back pocket when she sits down that sometimes inadvertently causes a number to be dialed.

I think “by accident “ in this sentence Because “by mistake” is more closely connected “your mistake” It will be used in this case below You press the number wrong , and it calls to not a person you were supposed to call then you can say “I miscalled by mistake”