You have to contact your Telephone Exchange for this error,the error which be like this" The password you have entered is not correct. Please enter your password again.(SBL-DAT-00569)"which means that there is a problem in underground communication although you have good network but for this selfcare problem ask your exchange to see your required parameters on your line in their system,securly they would find maxium voltage in the line.I came to know about through my telephone exchange.