Customer's Paymethods

Hi,

I'm working with DI API, and I have a problem with Customer's Paymethods.

For example:

Customer:

Contado: ckeck True

Bimensual:ckeck True

When I use this code:

Set oBusinessPartners= oCompany.GetBusinessObject(oBusinessPartners)

oBusinessPartners.GetByKey vsCarCodeCliente

oBusinessPartners.BPPaymentMethods.PaymentMethodCode = "Trimestral"

oBusinessPartners.Update

The result is:

Customer:

Contado: ckeck False

Bimensual:ckeck False

Trimestral:ckeck True

How Can I maintain selected all paymethod into the customer?

Thanks in advance!!