Re: Non EU B permit not linked to employer, changing work
First - do you have a permit already? If so what kind, for how long and with what conditions?
Second - a work contract is not just a piece of paper, but a binding agreement. If you signed and returned the contract from the first employer, you are obliged to take up the work and cannot just not show up. If you don't want to do that, you need to hand in notice as per whatever is regulated in the contract (in the first 3 months of employment, this is usually a week only, though it might be more). Alternatively, you need to reach out to the employer and discuss openly and honestly as to why you changed your mind; they might then just let it go, though again, they are allowed to insist for you start working as agreed and hand in your notice as agreed.