hobbitus I would like to send messages and replies from the one which is cheaper without disclosing that it is a different phone number
So you want to text people/organizations without them realizing you are using a different number?
But surely, if the recipient gets your text messages, but it isn't listed as your usual identifier, let's say Hobbitus, but it comes up Number Witheld or similar, they will still: a) not immediately realise it is from you, so will be surprised when they realize it is from you, and b) they will wonder why you are texting to them on a Witheld Number, which will also make them wonder what the eff you're up to :)
Anyway, moving on ...