Accessibility apps for live calls?

Accessibility apps for live calls? I have strong blocks at the start of sentences, this makes it hard to answer or make phone calls. Words like Alo, Hello, etc .. at the start are very hard to get out. I thought i could pre record these words with my own voice and use them on demand on live calls. so for example i would have single words on dial numbers that when i press; it plays on the live call. Are there any mobile app or specific phones that could achieve that? things like soundboards doesn't work cuz it plays from the speaker and even if the caller could hear, it will be very unnatural. it needs to be pushed into the live call not played through speakers.