Apple India — bad product service and false repair charges

Address: 700055

I have submitted my iphone 6 on 27th JUly 2017 in one of the apple authorized service centres at address:
Systematix Media (Store no: A 210, City Centre, Salt Lake, Kolkata-700064)as I was getting some sudden display issues.I have paid repair charges of Rs.12900 in advance.After one month I got a response from provider that the device is damaged and cannot be repaired.
It has to be replaced with new phone.I had refused replacement at that time and I was refunded only 10000 in cheque.Rs 2900 was deducted from the paid amount.I received a letter from Apple bangalore headquarters that after inspection issue found was different from the problem reported while placing repair request and there will be no cost for this repair request but still some money was deducted.
Request your help here and want back the refund of my money.They kept the request pending for more than a month.Please contact on my number [protected]/[protected].I got my phone repaired at Tech Recoil for Rs 6000 and it is fully working now.Only LCD was broken and has been replaced .Rest all was fine.I also want to know why Apple could not provide me proper service and why the service is so poor?They cannot identify the issues in their own product which a local service provider can also identify and resolve.Apple being such a big brand does not know what is wrong with its own product and only charge unnecessary money from its customers and try to sale new product against repair requests and that too at full price.