Mobile exchange may I demand it back?

Ho
2

I exchanged an iPhone 7 for a Huawei over a month ago. I wanted to have 50 euro left for the iPhone and I did not get the Huawei cover for this today. Now I said I want to have my iPhone again, but now it turns. What can I do? I have the purchase contract at home and the carton of the mobile phone I can ask for back then?

Am

If it is agreed in the purchase contract then you can demand it. If necessary, also with a lawyer

Ho

There's no sales contract, it was exchanged privately, the purchase contract is right where I bought it in the store