Superbalist Incorrect Sizing and Exchange Rejection

I am frustrated with Superbalist,

I placed quite a big order with Superbalist which included 1x Roxy Costume, Long sleeve, Color garden Onesie for my 8.5 yr old daughter as well as 1x Long Sleeve Rash Vest for my 3 year old son.

When I received the products I immediately thought that they looked small. I called my kids, held it up against them and could see that it would be a very tight fit on them.

Here is the thing, I used the SuperB size Guide that is provided with the item(s), as the Roxy costume alone is a R999.00 (it is allot of money!).

However, I messaged for a exchange straight away explaining about the problem (that both items-are too small) stating I know that exchanges aren't normally possible with Swimwear but could they please take this into consideration. The costumes have not even been put on as I saw straight away they looked small.

My main concern is the Roxy Costume. The Rash Vest was about R159 and I could re-gift but a R999 costume, that was incorrectly purchased due to the information stated on the Size Guide. I feel that the rejection for exchange is not fair. Now they only have 3 sizes left of the size 10yrs Old Roxy Costume, which I really need to order. I am nervous to, because if it is smaller than stated that is a R2160.00 fall out for me! Have a look here at the comparison:

I ordered a Size 9yrs Old Roxy costume for my 8.5year Old Daughter and a Size 3-4yrs Old Rash Vest for my 3yr Old Son.

Have a look at the Size Guide Compared to my Children (Who are, fit and average size, children for their age)

My Daughter: Height SuperB 8yrs: Height Super B 10yrs: Height

My Daughter: Chest: SuperB 8yrs: Chest SuperB 10yrs: Chest

My Daughter: Waist SuperB 8yrs: Waist SuperB 10yrs: Waist

My Daughter: Hip SuperB 8yrs: Hip SuperB 10yrs: Hip

My Son: Height SuperB 3yrs: Height SuperB 4yrs: Height

My Son: Chest SuperB 3yrs: Chest SuperB 4yrs: Chest

My Son: Waist SuperB 3yrs: Waist SuperB 4yrs: Waist

Upset, Honest Customer.