scam due to WhatsApp hacking

I received a message from a number registered to a friend. They asked me for money, and I trusted it was my friend writing to me. I sent the money, and minutes later she called me upset to say her phone had been hacked and it wasn't her who asked for the money. Sadly, I lost my money. Later, the same people called me pretending to be from Tigo and asked me to log into my WhatsApp. When I told them no, that I knew it was a scam, I closed it and checked my phone. They had sent me a code to enter into WhatsApp. I assume that's how they hack your WhatsApp.