One reason why your voice may be quiet or muffled when using the Melomania Touch for a phone call, is that the bands on the earbud may have been fitted so that they obscure the microphone hole. When fitting your fin bands, check that each microphone hole is aligned and not obstructed.
When replacing the band, please ensure the top of the band is pointing inwards towards the ear. The notch in the top of the bud and the microphone hole at the bottom should also align with the corresponding parts of the band. This ensures that the call quality and Ambient Mode functionality will perform to the highest standard.