Egg shell found in egg Mc****in

I had found bits of eggshell in an egg mc****in last year(end of October). This was surprising because it was quite a bit which would have been difficult for the person preparing it to have not noticed and it was not busy to have excused the poor preparation. Upon reporting it to one of the staff, she simply looked at it and did not respond, so I said that she should tell the manager, IF they care and then I left. I later posted a complaint on their website. this lead to a phone call from the branch manager which was unpleasant and then a call from Bella from their customer care who apologised and promised to send me a voucher. While my aim was to bring awareness to this hygiene issue and not to score a freebie, I was quite disappointed with their customer service. After sending them my address, I have not heard back from them nor have they delivered the voucher!