Bitcoin does not create a room for refund of bitcoin. But majorly it is rare for there not to be delivery of your fund though. Every merchant has a wallet to check the correspondence of transaction if there's any issue.
Because bitcoin transactions are not reversible, that's why we should be careful making online transactions. Even tough they can figured it out that there is accidentally deposited but because of anonymous identity, they can never trace where it came from and doing that is just a waste of time.
Having used of bitcoin through online transactions is very efficient and only spending a little time just to finished a certain transaction. And with this, we can maximize our time in some other works and we are very productive everyday.