Accept or Decline Conversion at ATMs in Colombia - What should I choose?

I hit “Accept” on a Servibanca ATM in Cartagena because I thought it would lock in a known amount in AUD. Later checked and saw the exchange rate was horrible - about 11% off. Felt ripped off. Used Scotiabank Colpatria next time, declined conversion, and Wise gave me a much better deal. Rule now: always withdraw in pesos (COP), never in home currency. Similar thing happened at Banco de Bogota ATM also, but did not accept conversion. 

BBVA and Colpatria ATM both said something like “If you decline conversion, your bank may charge unknown fees.” Total scare tactic. I declined, and Revolut converted at real mid-market rate with no extra fee. If you accepted and got a bad rate, that’s sadly how these machines make money. Never trust the “safer” sounding option.

Used BanColombia ATM at Bogotá airport and made the same mistake - clicked "Yes" for the currency conversion. It gave me a terrible GBP rate, plus a hidden markup. Later tried Davivienda and BBVA, hit “Decline” on DCC, and Monzo handled the conversion perfectly. Lesson: DCC = SCAMMY, local currency = best.

I withdrew at a Davivienda ATM in Medellín, and it asked if I wanted to be charged in USD  sounded safer, so I hit “Accept.” Big mistake. Got a rate of 3,300 COP/USD when the mid-market was around 3,700. After fees, I was down 12%! Always hit “Decline conversion” and get charged in COP  your bank will almost always give you a better rate.

Servibanca ATM charged me 22,500 COP for withdrawing 1.9 million, and another 30k COP via conversion fees. Used Wise Visa. Wouldnt recommend.

Even after declining conversion at Davivienda, I was still charged extra - feels forced. Used Payoneer Mastercard Debit.

Regularly use Davivienda ATM in Colombia with a Visa Debit card. Although it shows a 15,000 COP fee, if I decline conversion, Ive never actually been charged.

Popular Bank in Colombia allowed us to withdraw 1,000,000 COP with a fee of 20,200 COP using Mastercard.