The PIN that you were asked was a 4-digit call-in-PIN and NOT your account password .
You can access it (set it/change it) this way ...
while logged in > press the "Customer Info & More" tab > "Account Security Information" link > bottom right where it says "call-in-PIN" .
(sidenote: NEVER give your password to any company representative , it is is YOUR personal password , it should NOT be revealed to anyone , if someone asks for it ... it is probably a scam)
Regarding the promotion phonecall , maybe it was somewhere in the terms of the Buy.com offer (which many people abused by not buying anything and just registering a name) . I've been GoDadding for some time now and they never contacted me by phone .
Regarding the while-buying-promotions , I think it is very logical that a domain registration company wants to promote their other products and services too , mainly for two reasons ... many people are looking for those services also but don't know exactly where to find them (or their specifics) and secondly because selling those products helps a lot in keeping the domain registration prices low . If someone wants to he can choose fast checkout , where only a couple really relavent promotions appear (private registration and sometimes alternative extensions bundle offers) .
I would suggest GoDaddy for the best combination (so far) of good product (registrations) , security (big , respectable company in the domain industry) , good other products (eg. hosting) , nice prices (try googling or yahooing the word "domain" for a $6.95 offer from GoDaddy) , extremely easy "push" function and nice customer service .
Before some people reply with GoDaddy this and GoDaddy that , I'm stating that this is my personal opinion and that I'm not affiliated with GoDaddy ... just a happy customer . If you think about it , it is the company that played the most significant part in making domains easily accessible to the public (and also promoting the domain industry as a whole) in the new domain era (after the bust) . Also you should bear in mind ... the company has the right to keep strict policies regarding some issues (eg. phishing sites , spam sites etc) so as to protect its brand amongst other things (customers , internet safety , etc) ... in millions and millions of registration a small number is bound to have some problems ... customer service agents are humans and can make mistakes .
Of course , what I said above does NOT mean that there aren't many other very good registrars (or that I don't use other registrars also) . On this matter , it all goes down to personal preferences and specific needs .