Disappointed & Stressful!

I order the Montego toilet and Basin on 31st August, the delivery was quick but i was missing an item. They forgot to send me the toilet! I email them straight away, quick to response to my complain but then after a few days she starts ignoring my emails. I tried to refund the item but they want me to just keep the item and they will refund me £85 when i paid for £300! It’s so not unfair because the item is useless anyway without the toilet. So i called them and i spoke to a lady. I told her that i just wanted the missing item, the only reason I requested a refund is because the other lady is not replying to my emails. She said she will chase it for me. So now I’m not sure when will I actually received my item. This situation is very frustrating. I had to cancel my plumber and everything. I actually regret placing an order to plumbworld. I really hope they send me my missing item because I don’t want to loose my money when it’s so clear that it’s not my fault.