If you called someone by mistake You can say " sorry! I thought you are somebody else". And if texted wrong person than you can say.. sorry! I sent this to you by mistake. This was meant for somebody else.

Hi Dina, if you called someone by mistake, you can say: "Sorry I've dialed the wrong number." "Sorry I've called the wrong number." In case of a wrong message: "Sorry I've sent this to you inadvertently." "Sorry I've sent this to you by mistake." For more formal situations replace "sorry" with "apologies" in all of the examples.