Unfortunately, you often cannot have multiple phones with the same number. Many phone companies simply don't support it. One exception is a product called Verizon Number Share, which lets you receive calls on multiple devices, but it mostly supports wearable devices like smartwatches rather than additional phones.
@DawnSNAP wrote: My Indigo Card
We are a small charity with 3 people job sharing and needing to communicate with service users. Is there a way that they could each use their phone using the one mobile number so that they all see and receive texts and calls? They use iPhone.
I don't think so this is possible.