BSNL has provided various toll-free customer care numbers and e-mails to register complaints about the issues. You can also lodge an online complaint and further, you have the option to approach the higher authorities.
If your complaint is not redressed by these concerned wireless telecom companies and broadband/internet providers, even after the final order of the grievance officers (Nodal Officers, Appellate Authority) then you may file a complaint to TRAI, further you can appeal to TDSAT for the quality or standard-related complaints.