Drink spilt!

The other day I ordered a drink from Starbucks , that I paid R94 for. When my drink arrived it all was spilt out , there was probably less than half of my drink in the cup. I reported it , the came back to me a few days later & they gave me a R30! When I told them that the R30 is not acceptable as I couldn’t even drink my drink , I basically paid R94 for nothing. I was told unfortunately that’s the amount the refund for damaged items. How is this right , how is it fair ? It wasn’t my fault that the drink was half way done by the time it got to me ? Their customer service is just terrible.