As people have already said change some up in Airport for that day .
Banks are the safest bet .
Some money changers state they are licenced but are not , used one who tried to scam me reported to police and they said no crime commited as I hadnt lost any money and anyway I had dealt with an unlicenced dealer , sign outside said licenced !!!
If you use money changers make sure that the money is in your full view all the time , have a habit of keeping money in draw on desk they say for security , count it out bring it onto desk give it to you with a smile and thank you for your custom .
Sorry to say Bali is the only place in Southeast Asia that attempts were and have made to shortchange me .
Guess what never went back .