Calling vendors...

I don't think it's rude to say that your preferred communication form is through email. Then if someone does call you can let them go to voicemail and call them back on your break or after work

I'm sorry, that's totally unreasonable of your manager :/ I'm sure your vendors will understand if you say that you prefer email, or phone calls only during (whatever hours you aren't at work).

If they really want your business then they'll email you or call outside of your work hours as long as you tell them. So far I've only had one vendor want to call me and they agreed to call me back in the late evening when I told them my schedule constraints.

I think you could definitely tell them you prefer email, or to speak on the phone after business hours. You can't step out of your office to take a phone call if necessary though? I know my boss wouldn't care if I took some personal calls in the office but I still always step out when I do so... I just feel like it's weird to have personal calls when my coworkers can hear me lol.

I have a job where I literally cannot take my phone into work with me, so all my communication has to be through email and its worked out fine. It's actually nice to have a paper-trail of all the conversations if I'm every unsure of anything.

My vendors didn't mind when I said to email me instead. Where my office is located I get no reception in the building. That way I could at least keep an eye on my email and call when I go outside for lunch.