SHAFAQNA – The Grand Ayatollah Sistani answered questions about using guarantees for goods.
Question: If I buy goods in a non-Islamic country, and due to carelessness, I make them defective; considering that firstly those goods have guarantees, and secondly I damaged those goods myself; what must I do? Can I return those goods and use the guarantees which are given for probable defects in those goods or not?
The Grand Ayatollah Sistani: In these cases, you cannot return the mentioned goods.
Source: PERSIAN SHAFAQNA