Changing the payment method in the sermepa module to Credit Card only

[zand]

Hello,
I currently have the sermepa payment module up and running, and its offering my costumers the option to pay with Card & bank transfer, but we wish to have them pay only with card so the technical support said that we can control this by folloing this: "...Puede enviarnos el parámetro Ds_Merchant_PayMethods con uno de estos tres valores:

T = Pago con Tarjeta
R = Pago por Transferencia
D = Domiciliacion...."

No need to understand Spanish, they just said we should add the parameter Ds_Merchant_PayMethods to the module and select T for Credit Card...
I tried adding it like this:

$ds_merchant_order="1".time();
      $ds_merchant_data=zen_session_id();
      $total=$order->info['total'];             
      $ds_merchant_amount = round($total*$order->info['currency_value'],2);
      $ds_merchant_amount = number_format($ds_merchant_amount, 2, '.', '');
      $ds_merchant_amount = preg_replace('/\./', '', $ds_merchant_amount);
      $ds_merchant_currency = MODULE_PAYMENT_SERMEPA_CURRENCY;
      $ds_merchant_terminal = MODULE_PAYMENT_SERMEPA_TERMINAL;
      $ds_merchant_transactiontype = MODULE_PAYMENT_SERMEPA_TRANSACTION_TYPE;
      $ds_merchant_consumerlanguage = "001"; 
      $ds_Merchant_PayMethods = "T"; 

since that is the only place in the module that I saw ds_... I also tried 'T',"t" and 't' but this didn't work how and were exactly should I add this?

Thanks!

Thanks!