If you change number of nights stays you lose a substantial sum of money - the hostel we stayed in confirmed we would only be chsrged one night ( reduced from 4) - hostel of the sun in Naples - but we were then charged 67 euro on top of 35 euro deposit paid - so 103 euro for a sub standard / basic room stay. Terrible service a very deceitful. We strongly recommend not using Hostelworld or hostel of the sun in Naples.