Bharat Sanchar Nigam [BSNL] — fraud calls

Address:

Kota, Rajasthan, 324001

I just received a call on my landline from [protected] claiming that they are calling from bsnl. They said, they are updating my broadband connection but for this i need to send sms to 5667 with "bvas". I think its a fake call but the point is, how they knew my registered mobile number? My details are leaked from bsnl to scammers? Bsnl should look into this matter asap.