Is it permissible to withdraw from the sale of a device after its price has been agreed upon over the phone, and can the agreed-upon price be changed?

What transpired between you can be interpreted in one of two ways: either it was an understanding where the sale would not be concluded until the buyer saw the device, or the sale was completed based on description, with the buyer having the option of inspection. This matter is resolved based on prevailing custom. If custom considers it a sale, then you cannot retract unless the buyer agrees. If custom considers it merely a promise, then the sale has not been concluded, and you have the right to refuse the sale and change the price. A sale based on description is valid, and the buyer retains the option of inspection; if the sold item matches the description, the purchase becomes binding. For a sale to be valid, both the item sold and the price must be known in a way that prevents dispute. An absent item is defined by a description that distinguishes it from others, along with a statement of its quantity. A sale based on description for a specific device is valid even with deferred payment. However, if it is for an unspecified device (from similar devices), the sale is not valid unless the full price is paid at the contract session.