As far as i understand you have 3 different problems.
Issue with T-Mobile SIM cards discussed in this topic.
2
You couldn’t recive calls or you couldn’t make calls?
Take a look in this topics:
Take a look here:
You could have been found all that infos by yourself in the forum.
Hi Thomas,
now I got a new SIM card Type B/V7 from Telekom from which is written in a thread of OnePlus that it might be not killed. The problem is that you don’t habe influence on which kind of SIM you will get for substitution from the support.
I will inform you if it works or not…
EB
As far as I know, SIM cards with a “V” in the name are not affected. I think it’s important to insist on getting a new SIM card that works well for the OnePlus devices and to tell Telekom that the Fairphone is affected by the same problem.
Any update on this topic? @Douwe wanted to ask about it? 
I have a C/W2 SIM card from congstar and my ordered Fairphone will hopefully be shipped or arrive next week - and I don’t want to order a new card if necessary.
As far as I know the problem is known at the dev team and being investigated.
For now @Irina_Spitznagel advice above seems the best route.
As soon as I know more I’ll post here.
Sorry for not having better news…
Actually I think this is not a bug but expected behaviour. If you remove the battery, the FP has no way of advancing the timer, so inevitably the clock will be off the first time you start. As soon as the FP connects to a mobile network or the Internet though it should retrieve the proper time again. At least thats what my FP2 does after some time without power… 
Thank you for the quick response nevertheless
Affected cards will still last a few weeks if I followed this topic correctly. Maybe I just order a new card when my new phone arrives - according to congstar, all new cards do not have this problem.
My Congstar C/W2 survived about two months in the FP2. So maybe the Fairphone devs are quicker and you don’t even have to change your SIM (it’s more or less 15€). It didn’t die from one day to the other, the first disconnection problems started about one week earlier. At least if you call them, Congstar support is quite fast. I got the new SIM two days after my call.
I have a Telekom V2 SIM card and have not experienced any problems after two weeks. Fingers crossed. Should any problem occur, I will report it here.
I’ve got my new SIM today, unfortunately again a CW/7. My colleague from our IT department tried to convince T-Mobile to get a T6, but they didn’t. 
Fortunately i hold back my old moto G2 as a backup.
@Douwe: please give an update if there will be a fix available soon! Otherwise i will need to sell my FP2 and end this experiment.
Are you requesting a SIM card in Austria?
The Austrian Fairphoners are cooperating with T-Mobile Austria. If you like I can contact them for you and insist on a proper replacement SIM. It’s unfair if they don’t give out working SIM cards for FP2s (given that they also sell them themselves!).
No, it is a german T-Mobile SIM card. And it is a corporate card, so i’m limited to the will of the colleagues from our IT department, to discuss with the Deutsche Telekom guys. In addition there are so many other annoing bugs and issues in the FP2 hardware and software. That situation could be acceptable if there would be infos/announcements/feedback/plans or anything from fairphone.
Thanks for the info anyway.
Yeah, unfortunately we do not have a commitment by Deutsche Telekom yet, to provide functional SIM cards…
I’ve got an answer from support which i want to share :
The SIM card issue is indeed a known issue we are currently working on and that should be fixed for the next software update. Our software team already has the fix and is looking for the best way to distribute it.
So, I have got the same problem. Congstar and c/w3 in Germany. After 8 weeks, the SIM card was dead. I explained everything to congstar support, but I will only be sent a w3 again. I guess, I will have to move to another provider or use another phone.
This killed one of my SIM cards. The problem is not in the list of confirmed software issues https://fairphone.zendesk.com/hc/en-us/articles/207228996-Fairphone-2-software-issue-report and it doesn’t seem that 1.3.6 fixed it, either. So how can I know if / when this is fixed?
The update that @tkos referred to above is the one after 1.3.6. That’s all we know (i.e. nobody knows when it will be released).
Thanks. However, strictly speaking this has not even been recognized as a bug. If find that confusing.
That is correct, the official bug list is very small, i don’t like that too. But we have the bug list here in the community forum and at least a hopefull feedback from support now for this bug, which i had posted above. It seems that things are getting better now 
LTE contract no LTE (4G)