is old fashoined party line possible with 2 sims same number

I recently took an old 2008 tmobile prepaid line, changed it to an add on line on someone elses' account,
I bought my first unlocked smartphone, activated that line with a new sim from tmobile.
Is there any way I can use the old flip phone as a 'partyline'? I still have the old sim in the old flip-phone I've just turned the power off for now.
If. I turn on the old flip phone can I still make and receive calls ,aka 'old fashioned party line'? or if I turn on my old flip phone with the old sim with the same number will I ' brick' both phones?
help please , thanks in advance.....B) ????????

When you turn on your old flip phone the sim should simply stop working, since you moved the original line as an add-on to that other persons account. From my experience of moving lines, this alone shouldn't brick the devices.