Kent RO Systems Ltd — Invoice / difference is Product Price

Hi,
Yesterday i have purchased & installed the Kent RO (Grand +) Product. I directly co-ordinate one of the sales person Mr. Mohan Raj. I have received the warranty Card vide Product serial no. KR[protected] and have purchased the same for Rs.18, 500. At the initial discussion it was discussed for Rs.18, 000 but on installation date i have to pay Rs.18, 500/- I paid advance of Rs.2500 on 5th Apr 22 and the balance Rs.16, 000/- on 6th Apr 22 to the account of sales person. Mr Mohan Raj. The service provider name as mentioned in the warranty card is Universal Pure Water Solutions - Begur, Bangalore. I am following with the sales person from yesterday and was been told that i will receive one OTP which i need to share and only than i will get the invoices. Till date i have not received the invoice copy for my record. Really i am not happy with this type of service and have to incure additional amount of Rs.500 extra and also have to follow up for my invoice.

Will i get my invoice copy and the amount of Rs.500 which i paid extra.