My relative suddenly contacted me, asking for a quick loan of 3,000, saying they would pay it back tomorrow.

I said okay, and transferred the money.
The next day, they indeed paid me back, plus an extra 30, claiming it was interest.
I was quite touched: this person is reliable.
A few days later, they borrowed another 5,000, and again paid it back the next day, with extra interest.
The third time, they borrowed 10,000, and I started to hesitate.
They sent a message: "Don't worry, I never owe friends."
I didn't lend the money.
Half an hour later, I realized they had deleted me.
A few days later, I accidentally saw their chat list on another classmate's phone.
Everyone's name was followed by a number.
My entry read: 3000.