One's voice is The Ultimate Accessory.
Recall the greats: the gin-and-cigarettes Bacall, the Helen Mirren DCI Jane Tennison, the Cate Blanchett Queen.
Young women ignore this aspect of their presentation, and older women worry about wrinkles but ignore their voices.
Your mother may have advised "modulation". There's some truth in that. I heard a gorgeous young woman in her mid-20's at a restaurant; she screeched, "I'll have a slice-a peetsa and a dye-utt Coke". She sounded like Minnie Mouse through a megagphone.
Duchesse wants to march them by their collars to a private spot and hiss: Pay attention to the instrument that is your voice!
To a certain extent you are stuck with what you're born with, but you can make your voice more resonant and compelling by paying attention and using it consciously. ("Shrill", a criticism made frequently about Hilary Clinton's voice, is only ever made against women.)
If you have voice mail on your phone, record yourself most days and listen. Notice your intonation and pitch range. Identify the emotion you want to convey (warmth, enthusiasm, authority, confidence, etc.) and put that into your voice.
Listen to great voices; observe how the professional uses breath and the pause. Breath is the gasoline of the voice.
Notice how she emphasizes key words and phrases. She will (unless speaking a dialect) pronounce every vowel and consonant that is supposed to be pronounced, in every word. She will never, ever use the rising intonation at the end of a declarative sentence, known as "upspeak".
I don't support purging an accent, whatever it may be, unless people squinch their faces when you speak. That means, in any culture, "I can't understand you."