These people (Smart One Energy) keep calling. They use caller ID spoofing, which means that the number or name that is shown on your caller ID is not the number they are calling from. So if you file a complaint with National Do Not Call, make sure that you note the company rather than the number that showed up on your caller ID.
They are trying to get you to switch from Washington Gas to their company, but they misrepresent themselves as being from Washington Gas and saying that "you qualify for a discount" on your gas bill. Here's one complaint: http://www.ripoffreport.com/utility-companies/smart-one-energy-llc/smart-one-energy-llc-tricked-91a84.htm. Note that if they are from Washington Gas, as they say they are, then they should already have your account number. If you give them your account number, they will change your gas supplier to Smart One, with or without your permission.
Contact the Maryland Public Services Commission at 1-800-492-0474
Tell them
1. Smart One is calling you repeatedly
2. Smart One has not respected your request to be removed from its list
3. Smart One is using Caller ID spoofing to prevent call blocking and screening
4. Smart One is misrepresenting itself as calling from Washington Gas
5. Smart One is claiming that it is Washington Gas and wishes to verify your account number in order to trick you into giving them your account number