I want to use my bluetooth headset (Sennheiser MB660 UC MS) with an app that doesn't support bluetooth I work as a freelance consultant using a platform that aggregates my clients who buy hours from me in blocks. Billing is done per minute when a client makes a voice/video call. Voice clarity and noise cancellation is of the utmost importance. Clients are able to leave reviews after a call.

The problem is that the platform (two versions exist: Android and iOS) was built by a small startup who haven't invested in Bluetooth support (yet). As a result, headsets have to be plugged in to the the headphone jack of the device.

I invested in the rather expensive Sennheiser MB 660 since I was looking for the ultimate purpose built headset for knowledge workers. The trouble: I had assumed that all of its built-in noise cancelling microphones will continue to work even if I had a wired connection, and could live with that until the app added Bluetooth support.

HOWEVER, I belatedly discovered the MB 660's are designed such that Bluetooth AND the noise cancelling mics are switched off as soon as a wire is plugged in (some German engineering choices I find perplexing), and the only active microphone is then the one on the audio cable itself (not noise cancelling). Which beats the purpose of having such a sophisticated headset in possession.

Now that I have this headset anyway, and love it otherwise, I want to find a way to indirectly connect it to my Android device in a way that I am able to use it without connecting the wire. The only way to do that seems to be to plug something (henceforth, SOMETHING) in to my Android device's 3.5mm headphone jack. That SOMETHING will be a two-way Bluetooth contraption of some sort that can send and receive audio and able to pair with my headset too.

Does this SOMETHING already exist in the market, or will I have to make one? If I must make one, what components do I need and how to do I put them together?

Thank you so much!
The MB 660 can be used in 3 different ways

Bluetooth: Here we are powered by ourself and handle NC using 3 microphones build in to the right earcup
USB: Here we offer the same performance as Bluetooth and could be used as an alternative for the customer smartphone
Analogue: Here we force OFF the Bluetooth and only drive the ANC circuitry for the speakers. Only the in-line omni dir microphone on the cable can be used for communications