Is money earned from telecom companies' offers - which stipulate charging a certain amount to win a sum of money while fully utilizing the charged balance - considered permissible or impermissible?

If topping up a balance is done without need, merely to win prizes, then this is gambling. However, if the top-up is for a need and the balance is used, then there is no harm in it as long as the balance is received in full, and the intention of profit does not negate it when there is a need and the usual price, and this is considered among promotional incentive gifts.