If something went wrong

Find your situation and start at step one. Speed matters more than getting it perfect - especially where money is involved.

Money has left my account

Call 1930 right now. Do this before anything else - the first few hours are when a transfer can still be frozen.
Also file a complaint at cybercrime.gov.in. The phone call and the written complaint are both needed.
Call your bank on the number printed on your card and ask them to block the account or card.
Do not accept any call from someone offering to 'recover' your money. That is a second scam aimed at people who have already lost once.
Keep screenshots of everything - messages, numbers, transaction IDs. Do not delete anything.

My phone is lost or stolen

From any other phone or computer, open google.com/android/find (Android) or icloud.com/find (iPhone). Mark the device as lost, which locks it.
Call your mobile operator and block the SIM, so nobody can receive your OTPs.
Change your Google or Apple account password from a different device. This signs the phone out.
Block the handset by IMEI at sancharsaathi.gov.in, so it cannot be used with any other SIM.
File a police complaint. You will need it for insurance and for the IMEI block.

I clicked a link or installed something I should not have

Turn off Wi-Fi and mobile data on that device straight away.
From a different device, change the password of your email first, then your bank and UPI apps.
Uninstall whatever you installed. On Android, also check Settings ▸ Accessibility ▸ Downloaded apps and remove anything listed there.
Check Settings ▸ Apps ▸ Special app access ▸ Device admin apps and remove anything unfamiliar.
Watch your bank messages closely for the next few days. If anything moves, call 1930.
If you are not sure the phone is clean, back up your photos and do a factory reset. It is inconvenient, and it is certain.

Someone has taken over my account

Try the account recovery page for that service - Google, WhatsApp, Instagram and Facebook all have one.
For WhatsApp, simply reinstall and log in with your number. That signs the other person out immediately.
Once you are back in, turn on two-step verification and remove any linked devices or sessions you do not recognise.
Tell your contacts, publicly if you can. The person who took the account will be messaging them asking for money.
Change the password of the email connected to that account too.

Someone is threatening me with photos or videos

Do not pay. Paying has never once stopped it - it only proves you will pay again.
Do not delete the messages. They are evidence.
Report at cybercrime.gov.in. There is a category for exactly this, and it can be reported anonymously.
Call 1930, or 1098 if the person affected is under eighteen.
Tell one person you trust. The threat only works while you are handling it alone, and that is what they are counting on.
This happens to a very large number of people. Nobody who matters will blame you for it.

Still stuck? Ask a person.

If your situation is not on this page, or you have followed the steps and something still feels wrong, send an email describing what happened. Say what you clicked or installed, roughly when it happened, and what you have already tried. Do not send passwords, OTPs or card numbers in the email.

Write an email