Help needed please!

So I have a dual Sim Moto g4plus on Spark. It works fine. I rang up and had voicemails of both numbers permanently removed.
The problem is: the voicemail notification from Sim 2 keeps popping up.
Things I have tried:
1. Put Sim 2 into another phone.
2. Contact Spark.
3. Phone services and message data and cache reset ( settings>app).
4. Factory reset.
5. Root.
6. Rom flash. Currently on Android 6.01
7. Google.
I have to say that none of this worked. The voicemail notification still keeps popping up.

Is this little notification fellow actually hiding in the Sim card?
I just can't imagine it.

Any hints please...