Is it normal to get no confirmation letter?

Hi,
Not sure if I have been told the wrong thing, and hope some one could advise?
I was already in the Support Group (having appealed a decision to place me in WRAG) when I submitted another ESA50 form way back at the end of last year/ beginning of this year. heard nothing at all from Atos or the DWP regarding whether I would be called in for a medical etc, so last week I decided to call Atos to see where things were up to (the whole waiting game was making me anxious and worsening my condition). Atos told me that I would not BR called for a medical and my info had been sent to the DWP for their consideration late Feb, and they suggested calling DWP. I called them and spoke to a lady who told me it looked like I was staying in the SG (she said they got the info from Atos on March 6th but I digress) but could not tell me much more and told me to ring back in a week for an update ( I should mention I have had one letter from DWP but that was last week and related to an increase in April...apparently every one gets this). Fastforward to today when I called back the DWP... I spoke to a man who told me I was staying in the SG. Mercifully, I will apparently not be contacted for another medical for almost three years ( he could see it marked on the system).
I asked him when I would get a letter confirming I was remaining in the SG and he said I would not be receiving one (I was very anxious and exhausted during the call but he sort of made out the routine letter I'd received last week covered things...) I was I such a state that it only occurred to me hours later how I would have known had I not called today and been told over the phone that I would remain in the SG?! If I hadn't rung them how would I have known one way or the other?
I do not trust DWP to give accurate info and I am sure I should get some written confirmation of their decision? Surely?
Should I call them again when I have the resources and request one? I'm not sure I'm happy to just take their word for things on the phone. Should I just let it lie? And, what if I call and they refuse to send me written evidence of their decision? It really doesn't take much to make me anxious. I am so glad to remain in the SG and relieved I won't have a medical at this stage but I would be happier if things were more concrete / confirmed by way of a letter.
So, my questions are: is it normal to just be told over the phone when calling them yourself?
Is the guy wrong and should I request written confirmation? Shouldn't that be standard practice on their part?
How on earth does the DWP expect people to find out the outcome of their decision if they don't take the initiative and call themselves...? Seems weird, weird, weird...
I know from being non here that the DWP provides a lot of misinformation... I am kicking myself that it didn't occur to me to ask the guy today how on earth I was expected to know what was going on with my case had I not called myself...
The guy seemed pretty convinced I was staying in the SG for three years..we ll, a bit less than that... He said he could see it on the screen but should I just take his word for it?
I hate calling the DWP but I am very anxious now...
Thank you all for any advice offered....I appreciate it!
With the DWP it's never straightforward, is it?!
Ps.thanks to those who answered a question of mine last week... I appreciate it...I've not been on since to say thanks but I am always grateful to those who take the time to help!