Have I killed my rear calipers..

[VWKD]

After 3 years of advisories on low rear pads I thought it was time to change them. I went full steam a head with no research or reading pulled the calipers off and got the G-Clamp out to push the pistons in to no avail... I then moved swiftly onto the big hammer and drift approach and whacked the pistons in.. I then put the airline on them to check they moved out ok then whacked pistons back in with hammer.. then pads back in back on car, bleed brakes job done...

Then chatting to a mate just now he said ahhh those are the ones with the wind in/out pistons aren't they!!! which rings a bell from other VW I've done in the past but didn't occur to me at the time... would my whacking with a big hammer done serious damage that I need to be worried? the handbrake works ok as do the brakes though the MOT next month will confirm how well. Just a bit concerned now.

Cheers