Underpayment of ESA after Switch from IB

I wrote to the DWP on 22 March 2018 as I believed I may have been an affected individual because I underwent a ‘conversion’ assessment from older Incapacity Benefits paid on the grounds of incapacity for work. My switch was made in 2014 and I am pretty sure I was not considered for income-related ESA when I was switched to contributory ESA.

I have heard nothing from them to date

My question is would I have heard from them by now if I was entitled to a backpayment?

I no longer receive ESA.

Thanks!