Sling Money does not mark-up the rate of exchange between currencies. For most currencies, we use the 'real exchange rate' as published by CurrencyAPI.
We may use an exchange rate our local partners provide for certain currencies with less liquidity in the market. This is the case, for example, for most African currencies and some currencies in Latin America.
We do not mark up the rate when using a rate set by one of our partners. We always negotiate the best available rates with our partners to pass those savings on to our users directly.