[US] pretty sure my grandma has fallen for a scam

I owe Verizon 2,000 some dollars under her name that I’m waiting for T mobile to pay for. I confirmed today it’s not in collections. She apparently got a phone call from a debt collector saying Verizon sold debt worth 2000 some dollars she couldn’t tell me the exact amount. She told them her name and date of birth. They told her her social and confirmed that it was her social security number along with her address. Verizon told me it was a scam. She won’t believe me because they know her social. Verizon told me they don’t even have her number email or address so even if it was a debt collector they’d call me not her. I’m extremely worried that my grandma may be having her identity stolen now considering she gave them all her information. I have no idea what to do. When her husband tried to talk to the agency they told him they couldn’t talk to him and hung up the call. They haven’t called my grandma back since.