If you need to apologize to someone who hates you who isn't returning your phone calls, send a text message to the person. More than likely the person can't ignore a text message as it pops up on a cell phone screen. Remember text messages are only 160 characters.
Open your text message application on your cell phone. Type the person's name or cell number into the "To" box.
Explain in your text message that you regret what happened and you are sincerely sorry for your part in the situation. Inform the person you never intentionally meant to hurt her feelings and you promise to not do so again. Ask for forgiveness and close with the hope that you can meet in person for a more formal apology and conversation.
Send the text message when complete. Don't expect to hear back right away. Give the person a chance to think about your apology before they respond to you.