http://resolutioncenter.ebay.ca/
When you run into a problem (in this case Item Not As Described)your first step is to contact the seller. But this must not entail a long negotiation.
If the seller will not refund promptly (most will require that the disappointing item be returned and the buyer should use a Delivery Confirmed service) then the buyer stops communicating and goes to the above link.
If the buyer proves that the seller has the item back, he gets a full refund of his original cost. (But not the return shipping.) If it is the seller who is refunding, he may also refund the return shipping. Don't count on it.
If the seller still refuses to refund, Paypal will refund the original payment (only) to the buyer and go after the seller for their money. There is other fallout for the recalcitrant seller.
But you only have 45 days from purchase for this. That deadline is firm.
They last response was that they are not giving any refund to me and will ship this set soon even after me telling them I do not need it anymore.
They won't. They think you have no further tools.
Since 45 days have passed, go instead to the credit card you really paid with. Paypal is just a very useful mediator. Phone the 1800 customer service number and ask the clerk for a chargeback.
She will need your date of payment, currency used, transaction numbers etc. to process your refund.
I hope your credit card can help you.
Consider this to be a part of your life education. Most online companies have some sort of resolution process available, but most also have deadlines for this. You don't have to do it yourself and you don't have to reinvent the wheel.
You have up to 60 days to leave feedback for your seller. The most effective Feedback is calm and factual. 'Lecture notes incomplete and fake Refused refund Refused replacement' for example.
At the same time you will be asked to leave Detailed Seller Ratings. These are much more important. The normal Rating is five stars. The lowest Rating is ONE Star. No stars is a Free Pass.
If a seller's DSRs drop below 4.3, his ability to list and sell on eBay are greatly restricted, his fees may rise, and his seller account may be closed. So leave those DSRs immediately.
PS- If by some chance you get the replacement, which is unlikely, sell it on locally. Your course will repeat next year, eh?