Is SSDA legit or a ****?

Received an sms from Shapiro Shaik Defries & Associates (SSDA) on 28/11/2025 informing us we owe MTN money, and have been handed over to SSDA. Tried phoning SSDA and the phone does not ring just stops and goes off. Their whatsapps does not go through. And somehow they have our personal details, although the reference number does not correspond to our account reference number we use to have with MTN. It seems that someone at MTN is in cahoots. MTN let personal info out or someone sold it, and they are keeping quiet about it. Anyway SSDA seems like a ****. I did also send an email, no reply yet.