Serious Slippage, Yet No Trailing Stops Available

Oanda is a huge company, is such a shame they can't protect their clients from serious slippage and non-executed trades. Oanda told me that they will only guarantee me to fill within that slippage area during normal markets. But it just never happened. Worst of all, no trailing stops available after promising they would add it. At this point I should stop believing what they are telling me.