Get a call from this number anywhere from once a week to once a month. I say hello and there is no answer, just dead air.
"Justdial" has a listing for this number as a locksmith and gives an address in San Mateo... but that address is a small medical building. Since other people mentioned this number offering "home improvements," I would bet the improvement they want to offer in a new lock that they have keys to, so they can come and rob you at their leisure.