Delete that particular toon. Namechange could help but I wouldn't take risk.
I would defienetly delete that toon and any alts I would have in that banned toon guild I would slowly get away from there too. You're risking ability to not bg bot again in that account. Botting in bg is so safe that you had bad luck with 0.0001% chance.
1. He could ask for more money and couldn't bot ur toon for long time.
2. He could still report you and couldn't bot ur toon for long time.
3. You could report him but you wouldn't want to bot that account again for long time.
4. You could ignore him and couldn't bot ur toon for long time.
If you get reported blizzard first needs proof first so they put you under surveillance.first. Delete toon play it safe.