iD Mobile is for personal use only, not business.
5.3 You may use the Services only as set out in this Agreement and for your own personal use. This means you must not resell or commercially exploit any of the Services or content.
5.9 We are providing the SIM Card/eSIM and the Services solely for your own personal use (and not for any business purposes) and you may not re-sell or otherwise act as any form of distributor in respect of the SIM Card/eSIM, the Content, the Services or your number, code or any associated number. You must not connect a GSM Gateway to the Network or otherwise establish, install or use a GSM Gateway in relation to the Network or the Services without our prior written consent, which may be withheld at our absolute discretion.
If you’re using your iD Mobile phone service for business use, then you’re in breach of the terms of service.
https://www.idmobile.co.uk/help-and-advice/coverag
If there is ongoing network maintenance in the area then there is little you can do other than to use WiFi calling (where available), wait or switch networks (early termination fee may apply).