New Internet causes audio stuttering. How to fix that?

[conrado15 0]

Hi!
Generally speaking, for many years I have been using my local radio Internet, vatsim audio quality was very high. Now this ISP is ceasing transmission in a month so I in advance i changed to T-Mobile mobile Internet, and although the speed is 100x higher, ping the same (around 30ms) audio quality is unflyable. I hear stuttering in random moments, happening every 2 second, it sounds like this for example"Ryanair *stutter* J turn left heading *stutter* degrees descend *stutter* 0" instead of "Ryanair 34PJ turn left heading 320 degrees descend flight level 80". Missing those random key words in ATC communication makes it impossible for me to fly without asking 4 times for say again.
More details:
-New Internet goes from Huawei b525 router. Using Wi-Fi or Ethernet cable to connect it to computer doesn't make any difference.
-it isn't happening all the time. Ie. When i last took off from Manchester all ATC stations were 5/5, then midflight comes a moment when stuttering begins and it continues till the last controller, in Dublin in that case.
-controllers can hear my voice well
-when it starts happening and i disconnect from vatsim for a second and connect my previous radio Internet (ethernet cable coming from antenna on the roof) audio quality is back to normal. And of course, changing to T-Mobile and stutters return.
-restarting the simulator fixes an issue. For a while, because it often comes back after couple of minutes.

I am using FSInn. Windows 10 Pro. FSX Acceleration. Laptop Lenovo Y510P, Inter i7-4700MQ 2,4GHz, 8GB RAM, GeforceGt755m x2 SLI.

What I tried to do:
-moving the router away from electronic devices to avoid interferences - no change
-restarting the router, restaring FSFDT control pannel, reconnecting to VATSIM midflight- no change
-its the same on headset, and speakers (when headsets disconnected)
-changing the server from CZECH to GERMAN - no change

-disabling firewall and antivirus - no change

-forwarding port 3290 UDP in router settings - no change

-change to vPilot - same happens there.

Other than that, i have no clue, what makes this new 100MBit/s Internet (I have a good signal in my location btw) suck so much in transmitting audio messages. I'll be greatful for any peace of advice, if there is anything I can do with this Internet or should i look for another ISP...?