I am getting SPAM CALLS even after DND AIRTEL

Everyone is getting. Just ignore and hangup. 

use DND app and report. 

Unknown caller : Sir,.............

Me : 

Bro Dm Airtel On Twitter. I Also Done Same In 3 Or 4th Time Then Issue Solved

If it is not full DND, you will still get calls. So check that.

If not, download TRAI App and do full DND for all your sims. SPAM calls/SMS will stop after that. If not, you can report them. See this:How to teach lesson to Scam caller ? | DesiDime

You are getting because your number is shared in too many websites and with courier companies.

And organisations like banks.

All of whom have disgruntled employees or partner organisations with whom data is shared on good faith basis, but data is stolen or sold.

For complaints, dial 1909.

But before that, check whether complete DND is active or select DND is active.

All Telecom operators earn a hefty revenue from these bulk telemarketers. So they are not serious in taking action against them and on the contrary try to protect them.

I have always kept my full DND active for several years and lodged a complaint for most spam, telemarketing calls and SMS. In some cases where the caller was an individual, they have even disconnected the number. 

But in most cases, they try to close the complaint saying that it's a service call. 

Don't expect much in this lawless country with lawless rulers.

Examples:

Police can easily trace a stolen mobile handset by putting the IMEI number under surveillance. They never do that unless it's a serious criminal case associated.

Stolen cars can be traced by putting chasis number under surveillance, they never do that.

All electronic fraudulent bank transactions can be easily prevented by promptly freezing the destination bank account, they never do that.

Only option is to keep blocking those numbers. For spam SMS, use SMS Manager to filter them out.