Terrible Customer Service , Very Dissapointed

I booked for a flight to Uganda and I was denied boarding because they needed a letter from my doctor but when I was booking for the flight nothing was mentioned, I requested the letter from my doctor and I booked again for another date when I was about to board again I was told that I need to have a return ticket otherwise I can't fly...I'm very dissapointed that non of this was mentioned to me and Ethiopian airlines refused to refund me my money for 2 tickets a Total of R7400 I keep calling their offices to know avail, I need my money back!!!!!