Well, one quick Google came up with this:
In order to pay the traffic notice that you have received the following steps may be followed. The traffic authorities are reachable on the telephone number at the bottom of one of the traffic notice: 0034 902 508 686
1) You may ring this number and after you hear the recorded message in Spanish (do not take any options) wait to the finish and then you will get an operator.
2) Speak in English and then the operator will pass you to someone who speaks English.
3) Please, have ready your Passport number, The Num of Expediente (case number) of the fine (at the top right of the sheet ); also the date of the fine.
4) Please bear in mind that if you pay before 30 days have elapsed since the receipt of the fine, you only have to pay €70.
5) When on the phone they will provide you with the traffic office bank account details. eg. Iban and Swift number, for its use to pay the fine in a bank.
6) After the telecom the office will send you a copy of the fine to your home address, in your own language: English/Spanish and again it will say how to pay.
If you have further queries or want more clarification, we will be pleased to provide it.
Yours sincerely,