A contractor for the Boston Water and Sewer Commission lost a computer hard drive that may have contained customers’ information, the agency said. The contractor, Aclara Technologies LLC, cannot locate the hard drive, which may contain customers’ names, addresses, phone numbers, and account and meter numbers, the commission said in a statement Wednesday. The hard drive did not contain customers’ Social Security numbers, financial data, or state license or identification numbers, the statement said. Customers who receive calls from anyone claiming to represent the commission and seeking confidential information are urged to decline.