PayTM - Disallowance of my cashback at paytm

i purchased suzuki access on **/**/**** and i applied the promo code worth rs.**** (which states that **** flat cashback and * coupons of *** each for paytm mall) i showed it to suzuki executive and made the payment
they disallowed my cashback stating that i didnt applied promo code
should i take a screenshot everytime i apply a promo code..they know customer wont be able to prove it and thats how they loot customer like me
after talking to their customer care,which is the worst you will ever see, i talked to their senior official mr.manish too..but they all utter the same thing again and again ignoring everything you say(I attached a proof of it too)
They finally agreed to provide **** cashback but straight away neglecting ₹**** coupons.
these cashback schemes are just to defy the customer..why would i even use paytm if i didnt wanted cashback..they have * cashback options atleast i should be given one if my case is in dispute..and am ***% sure i applied the code yet they are straightaway declining my request
its their system's fault if its not picking it up my code.. i am battling with their customer care ..why would i care if i didnt applied or didnt wanted the cashback..these cashbacks are just gimmicks..they serve only one purpose which is to attract customers and looting them