Dell India — poor customer service and issue is unresolved

I had an issue with my dell laptop. I went to dell exclusive store at mgf megacity mall, gurgaon (Haryana). I thought that dell store is most trustful to repair my laptop. Firstly the attendant, he charge me 300rs to identify the laptop issue. After service, he told me that your motherboard ic is defected which need to be changed and it will cost me 2300. He told me that everything else is working okay on my laptop, problem is just with ic. At the time of payment firstly he denied to take card even he has a card machine. Earlier he had taken my card to identify the problem but this time he forced me to go and bring cash which was the very inappropriate behaviour of him. After repairing, he gave my laptop by saying that there is no any further problem and you can take your laptop at home. At the same day when i checked my laptop at home some particular keys of keyboards were not working. Day, after i went again, to told him that earlier all keys were working but now some of the keys are not working. He started arguing with me that it's not his fault and responsibility so i said firstly you charge me for full servicing to identify the issues specially for which i paid you including the other issue charges and now if any problem is occurring then that mean it is from your end which you need to resolve it. Anyhow after a long discussion, he took my laptop and after few days when i called him to asked about laptop then he said that which keys you told were not working is now working but other few keys are stopped working and if you want to repair them you have to pay more. Now, what should i do as my keys were working before even i gave my laptop first for problem identification then he did not tell about any keyboard issue and also assured me before giving my laptop that everything else is okay. Now, he did something that some other keys are not working which is a fault from their end. So, please take action and make my laptop repaired fully as soon as possible. Hence, i need a proper support from your side to resolve this matter asap.
My invoice no. Des/[protected]
Date of invoice:- 22 jul-17