No.
In your current billing cycle,
- regular transactions -> 17.5k
- purchase something -> 30k
EMI conversion -> -30k
- EMI 1 -> 5k.
- Total = 22.5k
- Available credit limit = 75k - 30k - 17.5k
In your next 5 billing cycle,
- regular transactions -> x
- EMI n -> 5k
- Available credit limit = 75k - (30 - 5k*(n-1)) - x
In the biling cycle after that
- regular transactions -> x
- Total = x
- Available credit limit = 75k - x
Your available credit limit is the only thing that changes. For this cycle, it'll be 75k-30k. Since you'll pay the first EMI this cycle, for the next cycle, the limit will be 75k-25k. The next cycle it'll be 75k-20k and so on, till all EMIs are paid.