Be patient. A month is hardly any time at all with fears like this. I think you're on the right track. If the sounds are never again followed by anything unpleasant and instead are followed by something pleasant or by nothing at all, she will eventually realize that. I'd make as sure as possible that no fuss of any kind follows a bell or phone in your house. Nobody running to answer, or yelling that someone's at the door. Bells and phones in your house should be things that cause no commotion. You could try, after a while, getting her to sit, showing her the treat but not giving it to her (this is to distract her from noticing the noise), and then have someone make one of those noises in another room. If she doesn't react to it, give excessive praise and the treat. If she reacts fearfully, ignore that reaction. Don't do the comforting 'oh you poor baby' stuff. Talk to her calmly in a normal tone of voice. She will learn that these noises aren't anything to worry about.
You may also want to consult with your vet. There are medications which can reduce anxiety and fear, and removing those helps a dog learn new behaviours.
I have a dog who reacts, or used to react, badly to various noises. She used to shake for 15 minutes if the car hit a puddle. I'd just talk to her in a normal conversational voice, saying things like' that was a puddle, no big deal, makes noise, not going to hurt you'. The words don't matter but the tone of voice does. It's been 3 years, but she no longer gets upset at many noises that used to bother her.