Either digital or analogue would probably give you the same trouble using a telephone due to the relative position of the microphone - to help matters, try holding the handset slightly away and forward of the ear until you find some improvement. Some people actually find it easier to remove the earpiece and do without when using a telephone. If you attend an audiology clinic, they should be able to advise you on this.
Not sure if that's what you're saying, but you can get a digital hearing aid on the NHS.
I believe digital aids are better (can't say from personal experience of using them), but I think they're programmable and therefore easier for a technician to adjust to your particular needs.
p.s. There are also telephones available on the RNID website which might make things easier - would your employers help you with this?