Vodacom refund

I've taken a contract with vodacom early October 2020. I've requested to cancel the contract immediately upon delivery as they gave me the wrong handset. It took 5 months for collection to take place & the order was officially cancelled on the 1 march 2021. Since October, they've deducted a total of R925 & now they only want to refund me R625. I want all my money back as I didn't even use the Handset.