they dont care about customers.. they shouldnt be allowed to do that or print it.
customers should have rights ,in this case you mentiones and in other cases like returning goods and getting refund, almost all shops in doha dont accept to refund your money, they will give you exchange period from 48 hours to maximum 2weeks..

why shops do that? why always the customer is suspect? are they afraid he'll cheat them or something.. thats not a business mentality,,,