Am I stupid....

My husband passed away a year ago last Thursday and I've been paying his phone bill for a year because I like to call his phone and hear his voice and even leave a voice message. My sister keeps telling me I need to move on and that starts with shutting his phone off and I'm being stupid. We were married for 11 years. I got married with parental consent at 17 and we weren't perfect but we spent ever day working on our marriage. We were doing so well. He died from a heart attack that was very unexpected. I know I should shut his phone off but I can't bring myself to do it. Whenever I'm feeling sad I just call his phone and hear his goofy voice mail and tell him how much I miss him... I feel kind of dumb...