Tracfone is interrupting voice calls with a message asking to move your service to a Verizon SIM. My young son has Tracfone service and I am now unable to call

Tracfone is interrupting voice calls with a message asking to move your service to a Verizon SIM. My young son has Tracfone service and I am now unable to call him reliably, or him call me. Since when can a carrier insert ads in your voice calls?