User Activity

So, i have 2 lucky mobile sims and plan to use them in one phone (iphone 13 mini).I see 2 options in the online portal.       "Transfer services to another phone " and "Transfer services" lands you to the same page where it asks for EID and stuff, so...
I am an existing lucky mobile user. Lets say my number is xxx-xxx-xxxx. I own another number yyy-yyy-yyyy with another provider. I wish to change my existing number xxx-xxx-xxxx but instead of being allotted some random number i wish to change it to ...