Online flight reservation

Booked myself a flight from Munich to Cancun with airberlin (902€ return). Not as easy & stress-free an online formality as it should be, requiring an additional 15' phone call to clear an unexpected 40€ seat-reservation surcharge in my bill, despite this being a free service for "topbonus Service Card" members (79€/year) - which I applied for so as to be allowed an extra 32kg of dive luggage free of charge, besides 30kg of check-in and up to 8kg of carry-on, including laptop.

Flight details:

06.03.2012	AB7414	13:05	München	Cancun	18:05
02.04.2012	AB7417	19:40	Cancun	Düsseldorf	12:25+1
03.04.2012	AB6031	14:50	Düsseldorf	München	16:05

PS: A month ago I could have booked direct flights both ways for 965€ return, but today those same flights would have cost me 1435€!

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UPDATE: Having received my "topbonus Service Card" by mail, I dutifully registered my dive bag & lights online as required, only to once again get an extra bill of 150€ despite this being a free service.

UPDATE: Finally got an email from airberlin apologizing for any inconveniences possibly caused and blaming a faulty registration. Supposedly the erroneously charged 40+150€ will be reimbursed.

UPDATE: Looks like both surcharges have been booked back.