seller didn't send me the correct quantity and paypal denied claim

[MaryRem]

I purchased from a chinese supplier (which i didn't know at time of order) product arrived after 10-12 days, I ordered 4 quantity and seller only send me 1 quantity, I exchanged several messages to seller but seller said they confirmed their colleague and send correct quantity, which I don't believe. Seller is so fishy that it mentions in paypal invoice that software services, however I purchased merchandise, seller invoice also fishy mentions 5 quantity instead 4 quantity bought. What should I do now? I can't further create case as paypal website says we encounter an issue now. please guide me. 

I also suggest seller to do atleast 50/50 refund, actual price i paid is 79.60 USD, and 1 quantity is 19.9 so I said seller to return 39.8 atleast but seller has denied that even

[kernowlass]

@MaryRem 

How do I open a dispute with a seller when a purchase goes wrong?

You can open a dispute in the Resolution Centre of your PayPal account within 180 days of payment if:
•You don’t receive the item
•You receive an item but it’s significantly different than the description on eBay or on the seller’s website

By opening a dispute, you can communicate directly with your seller to work out a problem transaction.

If you reach an agreement with the seller you can close the dispute. If you're still not happy with the result, you can escalate the dispute into a claim. We'll review the claim and decide on reimbursement.

These steps apply to Personal accounts. If you have a Business account, please log in to see the steps that apply to you.

To open a dispute:
1.Log in to your PayPal account.
2.Near the bottom of the page, under 'More about your account', click Resolve a problem in our Resolution Centre.
3.Click Dispute a Transaction.
4.Select the button beside the transaction you want to dispute, then click Continue.
5.Select ‘Item dispute’, click Continue and follow the on-screen instructions.

Note:
•Generally buyers must wait at least 7 days from the date of payment to escalate a dispute for an item not received
•Where an item has not been received, please ensure you have given the seller enough time before opening a dispute

https://www.paypal.com/webapps/mpp/first-dispute

DO NOT CLOSE THE DISPUTE UNTIL YOU HAVE A CLEARED REFUND OR YOUR ITEM WHATEVER THE SELLER SAYS. ALSO DON'T FORGET TO ESCALATE THE DISPUTE TO A CLAIM WITHIN 20 DAYS IF THE SELLER DOES NOT REFUND.

If that does not work then if you funded your paypal payment via a card then contact your card issuer and see if they will do a chargeback for you.