Help with stuttering at retail job

Help with stuttering at retail job I’m the assistant manager at a retail store and whenever a customer walks when we have to greet them and tell them about our deals. For some reason I can’t say it all, I used to be able to say it just fine. But every day is extremely stressful because i’m always watching the door and avoiding when customers come in. Also when answering the phone at work I always stutter, but when I answer it in front of a co-worker I never do! Whenever the phone rings I grab it and answer it near a co-worker so that I don’t stutter. Can anyone give me tips on how to be able to greet customers again. Thanks!