If a person who is not indebted to the transferor accepts the transfer of debt to himself, he can claim the amount of the debt from him before paying it. This is unless the debt that has been transferred to him has a period, and the period has not yet expired. In such a case, he cannot claim the amount of the debt from the transferor before the period expires, even if he has already paid it.
If the creditor settles what he is owed for a lower amount with the transferee, the latter can only claim that amount from the transferor.