具体的情况不是很懂，帮你稍微写了一下。

看看行不行。（注意回复的时候，把他们上次给OFFER 的那个邮件捎上）Your First Name Your Last NameYour addressYour telephone numberyour emailyour ID (reference)Dear Sir/MadamI’m writing to notify you of my decision to accept your offer to enrol in the …(your course) at…(your university).Thank you for your time and consideration. Please regard this letter as my formal acceptance. Unfortunately, as I checked my application status online, it remains…(pending or,把网上的那个状况写上去). 或者：There is no record of my application in the system(看你具体是哪一种情况）I would like to find out whether my application is successful,.Your help in this matter will be very much appreciated.Yours faithfullyYour name