Sorry to be pedantic, is your set up a Vitocal 200 ASHP feeding a Vitocell cylinder ( you mention Vitocell in your heading, or did you mean Vitocal?) and is the noise consistent and constant at all times or only when the pump in the Vitocal indoor unit is running?
If it is the former, I would get your installer back to investigate, I would guess it is cylinder set up / installation related.
If it is the latter, ie. only whining whilst the indoor pump of the Vitocal is running, it is possibly the three way valve (under the pump) that has not fully located into position. if you set the Unit ( if it is a M-E-AC) into cooling mode, the valve will move across its full range. Then, after 10 mins put the unit back into heating mode and the valve will reposition (and hopefully correctly seat) itself. If it is the M model switch it off for at least an hour then repower the unit. During the repowering / set up phase it will movevthe valve across its full length of travel.
Having said all that, if you have a Viessmann Vitocal ASHP feeding a Vitocell cylinder (or indeed any other manufacturers cylinder), I would contact Viessmann and raise the matter as a warranty issue. The Vitocal is sold on the basis of it’s very low external noise profile - but most people would also expect the internal unit to offer the same level of non intrusive noise. I have only fitted one Vitocal (a high temperature 300), which was fine, but noisy (the external unit) as most high temperature units are. However, I believe that a very low humming noise from the three way valve not seating correctly on the low temperature units ( the 200 and 222 series) has been an issue on some units.