HOw to handle multiple dependable input fields??

Hi,

How do i structure the following within one form:

I have 3 services which have a period and a payment radio options, so i created 3 fieldsets, one fieldset for each service and 1 general contact form.

So how do i make sure one of the service is selected with both radio values.

for example

<fieldset>

		<legend><strong>Service A*:</strong></legend> 
        <p>
          <input name="prod_flatfee" type="radio" value="250">
          250,-<br />
          <input name="prod_flatfee" type="radio" value="225">
          225,- <br />
          <input name="prod_flatfee" type="radio" value="175">
        175</p>
        <p>
          <input name="payment" type="radio" value="paypal">paypal<br>
          <input name="payment" type="radio" value="google">google</p>
        </fieldset>

Code (markup):

Any tips, suggestions