I have been leaving my C240 for services only in F...

I have been leaving my C240 for services only in Feldmann till date and I am thinking of leaving it in any other service centres as i find the depreciation of the quality of the service in feldmann. I am doubtful off the service they are doing. I did my A service in April and when I left the car for winterised check up, i find there are something which was billed replaced with new parts during A service is again due for service, Like Air filters, Some Joint boots etc. I am seriously Doubtful whether they have serviced my car properly.