Hey Peter,
Yes you better change the number…the problem is that your number is not with only one but many.
This happens because you have registered on some Ad, but this Ad was from Affiliate(this is how they call themselves). After that they give your number to many brokers, so the first that succeeds to deposit with you, will pay the to Affiliate. Overall the Affiliates are the once making the sweet money.
Keep your head up always when dealing with anyone over the phone.