Log into MeinVodafone. Under My Account, click Login Information. Then change / activate the phone number on phone number. Enter your mobile phone number. You will receive an SMS with a 6-digit code. Enter the 6-digit code.
You can see your contract term in MeinVodafone under My Tariff. Are you using the MeinVodafone app? Then you can see your contract period under My contract > My tariff. Tip: You can also find your contract term on your invoice.