default phone number selection in android 7.0 is lost after exchange sync runs


AC Question

I have many contacts in the exchange account (office 365) that sync with my phone (Galaxy Xcove 4 Android 7.0).

When I select a contact and chose a different default phone number the phone selects it and it is shown for a couple of seconds. Then after the sync with the exchange account the default phone is back to the first one in alfabetical order (many times this is fax..)