Unfortunately, we do not have service centers to repair products.
A defective product should be replaced by your point of purchase during the warranty period.

We offer a 'return to retailer' warranty on our products. In case of a defect, you can return the product to your retailer with failure description, proof of purchase and all accessories. During the warranty period you will receive a replacement product from the retailer if available. For full warranty conditions you can consult: https://www.trust.com/support/warranty

For Bluetooth the maximum range is listed.

The maximum range is reduced by the interference of the environment where you use the Bluetooth device.

Sources of interference; these things can cause interference with Bluetooth devices if they are nearby.

• Microwave ovens
• Satellite dishes
• Electrical sources like power lines, electrical railroad tracks, and power stations.
• Cordless phones
• Wireless video transmitters
• Wireless speakers
• Certain external monitors and LCD displays
• Wireless cameras
• Baby monitors
• Wireless devices from other people, e.g.a neighbor's Wi-Fi device.
• Poorly shielded cabling
• etc. etc.

As of iOS 11.2, when you are using a Bluetooth headphone and receive a phone call, the button that you use to pick-up the phone call, determines which device is used for the audio.

If you pick-up the phone call with the green button on the iPhone display, then all the audio will be handled by the iPhone microphone and speaker (and not with any connected Bluetooth device).

If you pick-up the phone call with the call pick-up button on the Bluetooth device (headphone or speaker), then all the audio will be handled by the Bluetooth device.

If the person that is calling you cannot hear you – or the other way around – it may be possible that you picked up the phone with one device and are talking via another.

Use the audio icon on the iPhone display during the phone call to change the audio device.