Hadith.3806 - Hammad narrated from Al-Halabi who said
I asked Abu Abdullah (as) about a man who bought a garment and then returned it to its seller, but the seller refused to cancel the sale except with a reduction in price.
The Imam (as) said: "It is not permissible for him to take it back at a reduced price.
If he was unaware and took it back, then sold it for more than its original price, he must return the extra amount to the first seller."