Bad service

I made my first purchase on ubereats app used first time order promotion of 75% got chicken licken buy 1 get 1 free (R65 each ) I bought 2 amounted R130 Promotion 75off then was R55 Charged R17 plus driver tip R27 Total deducted R100.69 Yet they say I'm owing R27.69 tip 🤔 Tried contacting them nothing has changed Bad welcome from them