I'm the same, used to work in call centres too so have a lot of experience communicating on the phone, but I just don't enjoy talking on the phone to friends. And with prospective dates and women it's even worse.
The problem is, women seem to love the phone!! Previous girlfriends kept me on the phone for hours! And calling new women and having awkward small talk fills me with dread.
Here's what helps me though. Walking. When I'm on the phone with someone new, I pace. This takes away any negative body language I could be having and makes you sound better if you're not hunched over in bed or on a sofa. Also, I have a list of 5 possible things to talk about, now it's not always necessary to use this list but if you feel the convo dying or there's an uncomfortable silence, you don't have to think and can just pick one of your 5 topics and roll with it.
Also, I like to make calls as short as possible, you don't want to be getting a hot ear, so say you have to run or have people coming over or anything to make sure the call doesn't drag on until a bore point. Leave them wanting more.
And like with most things, after you've done it, you feel a lot better for having done it and not pussying out. Which will make the next time less daunting.