Verifying employer for cell phone contract.

I have been with Verizon Wireless for about 10 plus years. In July, we switched to Smart Phones with a big increase in our costs. Now, I received a letter stating that the discount that I had been getting for being employed by one of the participating employers is about to expire. They want to me to send a pay stub or some other proof that I'm employed at one of their preferred companies. I never had to give them proof of employment when I started the contract. Has anyone else experienced this? It just sounds odd to me.