Recycled number

My Cell C number was on contract for 2 years, which expired March/April this year, I can no longer connect to Cell C's network, which means i can't receive or make calls or SMS. I don't know if my phone number was recycled, but I am very disappointed. Why can't it be changed to a top up plan? I didn't use the SIM card for approximately 3 month s, but as it was a contract new voice, data and SMS bundles were loaded on monthly. I have since changed to Vodacom, but would like access to my old number again.