Recovering internal memory data from dead HTC One M8?

A

AC Question

Recovering internal memory data from dead HTC One M8

I dropped my HTC One M8 due to which the phone has stopped working, the screen got cracked, it doesn't start and doesn't charge,

absolutely nothing.

I took the phone for repairing and they told me that, the phone needs following:-
1. Chipset rework to main board
2. Replacing the charging connector
3. New LCD unit
4. Software flash - all personal data will be lost/erased

I am more concerned with the 4th, the loss of data from the internal memory.

I have some important files, texts and WhatsApp messages(unfortunately not backed-up). I would like to know if there is anyway that I can recover the lost data.

I came across searching the internet that there are tools for recovering deleted files. So, is it possible that I get the phone repaired including software flash and then run one of these recovery tools viz. H Data Recovery to recover my data? I mean even with a software flash the data will still be in the memory and just the pointers will be removed, right? like it happens in simple disk format.

I am assuming this, please correct my understanding.
If the above is possible, what should I ask the repair center to not do, so that there is still the possibility of data recovery?