If she says it's a mistake and wants to go, you respect that instead of trying to convince her do what you want. If she doesn't pick up the phone, iether leave a voicemail or send a text one more time, but you don't call her three times in a row to try to force her to pick up. You don't go to the store looking for her when she obviously doesn't want to talk to you.

Leave her alone. If she wants to talk she'll talk. She's made it clear she doesn't want to hear from you and continuing to harass her is entitled. "I did nothing wrong" is irrelevant; people have a right to not want to be with you for whatever reason whether you think you're right or not. She's not wrong for not wanting to be with you either and she has a right to be left alone.