Unauthorized Credit Check and credit score impact

Uninvited I get a phone call from Cell C, wanting to sell a new contract and new phone. The lady was rude and pushy wanting to know where they must deliver the new phone - Work or home address. I was not interested, and then she puts the phone down. Next day I get notification that a (hard) credit enquiry was made after the call ended on my profile, which reduced my credit score. This was unauthorized, and now I have to spend the time to get this fixed! It was not me phoning Cell C asking after a contract. I am in the process of buying a house, and will hold Cell C liable. Also, Customer Care is not care- Sefakotsa would have sent me a reference number via SMS - I am still waiting. The team leader would have phoned me. Also, still waiting.