Tata Docomo — reactivate my tatadocomo mobile number

I was using [protected] tata docomo number. I didn't use this number from long time. I took this number on my college id card. Now i want to activate this mobile number. Please tell me the procedure to reactivate this mobile number. I have very urgent need to reactivate this number

Thanks & regards,
Navneet kumar
Current using mobile number: [protected]
Email id: [protected]@gmail.com