Wittycart — wrong item has been sent

I ordered high waist slimming panty from wittycart website.
It arrived on monday date : 15/07/19
Wrong item has been sent.
Not as per the picture shown while ordering.
It was supposed to be free size and black in colour but it's totally different from what we ordered.
Disappointed!
I want to return this item.
I've texted them through their contact in their website.
I've also reviewed their item in the website.
And i've sent several mails to them regarding this.
Once on thursday (18/07/19) they replied me asking what's the issue i'm facing with their product. After then i've sent 2 mails.
Till the date, no mail has been received.
At least they could have assured me that they are looking into the issue but nothing has happened.
I want reply as soon as possible.
How can i return this? And how will i get my refund of 1000 rs?