1) not sure why you have this code twice, the second line looks like it would cause an error:
mail( $to, "SBR Online Inquiry", $message, "From: $emailadd ");
mail( $to['center'], "SBR Online Inquiry", $message, "From: $emailadd ");
2) in your code i don't see where the $to variable is getting set, but to change it based on the selected radio button, you would need to create a switch case statement, example:
$to = "email@example.com";
case "SBR Rizal":
$to = "Rizal@domain.com";
you will need to add additional case statements for each possible radio button value.