The assembly line of the earbud is completely glued so you will have no chance at being able to put it back together once it has been thoroughly cut. You will also probably deeply skratch the surface which will make it uncomfortable to then wear in your ears.

You may try to pry through what seems a second access point on the stem of the bud. Unfortunately that is just aesthetic and will not help you access the inside at all.

Once inside you will notice that there is a very short ribbon cable connecting the motherboard of the bud with a daughter board on the stem. In the stem there are 2 of the 3 microphones and the proximity sensor.

The cable is so short that you probably already ripped it away in your effort to open the bud. The connector looks robust, however due to the extremely short length you will have no chance to re-attach it in position during re-assembly. Assuming you will be able to reassemble the bud at all you will not be making calls with it anymore.