[India] Phone hacked by calling on a number

So i just received a call from someone that they have been receiving messages from my uncle’s phone saying, “Send 45k on gpay, need to pay someone but my UPI is not working.” Now, they’ve sent it to almost all of his contacts which is causing a lot of chaos.

When I asked my uncle how it happened, he claims that he received a call on his phone that they have a courier and he needs to call on a number which involved hashtags. Can this be possible? Is there any way to tackle this? What are the things I should do next?

Thanks!