Hi,
The RateMyCallAllowCustomUserFeedback parameter does not dictate how often the user is asked to provide feedback on their experience. It simply allows them the ability to add a string of custom text along with their experience rating.
Instead, in order to adjust the frequency at which they are asked for feedback you will need to modify the RateMyCallDisplayPercentage parameter. Set this value to 0 if you don't want users to provide any feedback at all.
Also note that these settings are part of the client policy. So if you have multiple client policies in use across your organisation then you will need to modify these values in each of those policies.
Kind regards