Valid & Invalid transactions

"Price adjustment" when shopping online

Q: When shopping online (Temu etc.), certain companies have something called "price adjustment". It is a benefit which gives the buyer back the difference in his previous purchase compared to the current price which is received by the buyer as credit in his account. 

For example, I purchased an item for R70. One week later it is R50 on the same online store. Using price adjustment one can claim back R20 as credit only to be used on that online store. Is it permissible to take that credit?

Forgetting to inform the customer of the different sizes of the item for sale

Q: I sell products online through Etsy. I sold a desk mat through Bay‘ al-Salam. The mat has three sizes, but I accidentally forgot to add the size variations to the listing. The displayed price was for the smallest size, and I delivered that smallest size to the customer. I did not intend to deceive the customer; it was an honest mistake. The customer accepted the item without requesting a refund. 

Is the Salam transaction valid, and is my earning halal? Does the hadith that Allah has pardoned mistakes and forgetfulness apply in this situation?

Shopkeeper allowing one to take items and put the money in the till

Q: I work as a teacher at a Madrasah. The Madrasah has a tuckshop. When I buy from the tuckshop, the shopkeeper (an elderly Moulana) allows me to take what I want to buy and pay the money directly to the till. In fact, he told me to do this once or twice. There is no loss to the tuckshop in my doing this. Generally, the shopkeeper doesn't even know what I bought since I paid directly to the till. Is this permissible?

One's supplier delivering directly to the customer without one taking possession

Q: I want to ask -  is drop shipping permissible or not? Let me explain the process: 

When a customer places an order, I contact the supplier to say that a customer has placed a specific order. The supplier then charges me the cost of that product from my bank account and then delivers it to the customer. So in that way, is it permissible or not?

Buying a bag of goods without knowing its contents

Q: There is a app called Refreshi, this is how it works, you pay a certain amount and get a bag of food/dessert etc... but you don't know exactly what. This is how it is written. 

"Enjoy a tasty mix of baked goods. R68 You could receive, donuts, croissants, danishes, and/or pastries. Every bag is a surprise and delight to your tastebuds." 

Is this permissible?

Selling items on online stores with different payment options

Q: On Amazon and other online stores, there's a type of installment payment that involves interest. The buyer takes out a loan from the bank to pay for the product in installments, and the store pays the seller upfront without any interest. The buyer pays the installment to the store, and the store pays the seller the full price of the product immediately. 

It's not possible to disable this payment option on these stores. 

Would it be legal to sell on these online stores?

Dropshipping

Q: Is this form of dropshipping allowed: 

I advertise the product of a supplier with a 20% increase in price on my store. All products on my store have the same percentage increase from the wholesale price. I consider the 20% as the commission I receive. This has not been communicated with the suppliers, as there are many suppliers whose products are being advertised on my store. 

When a customer places an order, the product is shipped directly to them. The customer pays shipping fee. They are informed that I purchase the product on their behalf and take a commission, but may not know who exactly the supplier is, or how much commission is taken (they just see total price after commission added).