If the seller claims that he made a mistake about the price of the item, does the purchaser have to pay the difference?

There is nothing wrong with selling equipment that measures the levels of alcohol in the body

Ruling on exchanging an old phone for a new phone, and paying a sum of money in return for that

Ruling on using points offered by airline companies

Is it permissible for her to get an invoice for medication from a pharmacy from which she did not get this medicine?

Ruling on making phone apps for some educational projects and selling them

Does he have the right to take possession of a house that was bought with his money that he used to send to his mother?

It is not permissible for a dealer to sell auto parts that he does not have in his shop, because that comes under the heading of selling what one does not own and does not have in one’s possession

She makes cards for festivals and sells them – is that permissible

His friends ask him to buy computers for them and he adds a profit for himself