I assume you want to port your old number into Visible. Visible will not lock the old phone; however, once the port is completed your old number is automatically canceled by your current carrier. Your porting the line/account not the phone - so it's easiest just to signup with the new phone. You can use the old phone with another line if wanted.
You've then go two options - provide the port information at Visible signup or defer porting in the old number until after your account is activated with a new temporary number.
See the following for porting to Visible:
https://www.visible.com/help/how-do-i-transfer-port-my-number-to-visible
and
https://www.visible.com/help/carrier-list
The SWITCH25 promo code is the best deal going right now. Dont forget to grab a referral code from the Savings Spot or someone's posting history. However, if using promo code that referral wont be applied/stacked in many cases - you can specify both a promo and referral but should apply the promo code (you wont get the referral discount but the referrer would still get a referral credit).
