DislikedI did a trade inquiry... but they gave me an illogical answer: Cause to liquidity it was not possible to fill in your order!! What a kind of answer is it?Ignored
By contrast a market order will always get filled at the best available price in the market. That means a market order could be filled at the price you specified (no slippage), at a better price (positive slippage), or at a worse price (negative slippage). With market orders, execution is certain, but price is not.
It's important to keep in mind that during a major news event such is Non-Farm Payrolls there is less liquidity in the market to fill your orders. That means the chance of slippage (both positive and negative) increases and there is a greater chance of limit orders not getting filled. This is particularly true for EUR/CAD which is not a major currency pair.
I'm guessing that you wanted to trade EUR/CAD during NFP, because you saw the potential for huge price movements in this pair. However, it's important to keep in mind why the price is so volatile for this pair during major news events. It's because there is not as much liquidity.