This isn't going to be the best response ever. I had the exact same job doing customer service for a fulfillment warehouse, taking complaint calls for like five different products. The phone would ring, I'd state at it always giving it three rings, hoping they'd just hang up, take a big breath and pick it up. I suck on phones. The soft h in "hello" is one of my hardest sounds to start a sentence with. Hey, whatsup, to, all fine but not hello. I specifically remember a job selling phones and a boss riding my ass for introducing myself to customers at the door with "hey whatsup." The top salesman, this shark named Tyler, would always find the exact moment i got hit with a stopper to swoop in and introduce himself and I'm pretty sure I was let go because of my stutter. I was second from the bottom after two months but SECOND, they kept the bottom who showed up late every day. If you like the job you'll find your mental scripts that work, obviously slow down and take your time, you can only do the best you can.