Change from a trademark to a servicemark?

[patpro23]

In a nutshell, I filed a trademark when I meant to file a service mark for the same type of goods.

Details:
I filed a TM application directed to a particular type of product that I sell in my online store.  The specimen I provided was an advertising broshure (and webpage) showing the mark in use for the sale of these items.  I received a rejection based on the specimen stating that it was directed towards service as opposed to the goods themselves. 

At that time I realized that I should have listed the mark as "sale of" particular goods, as opposed to just listing the actual goods I sell. 

Question,
Is there any way to change my application from a trademark listing particular goods to a service mark listing the "sale of the same goods"?
I know you are not permitted to add/broaden categories after filing, but in this case I don't think i would actually be broadening the application.

Any advise on how to correct this mistake and/or applicable TMEP citations would be greatly appreciated.

[JSonnabend]

You can attempt to change your ID, but changing from "goods x" to "retail services featuring goods x" is changing the scope of the ID.  You will, in all likelihood, have to file a new application.

- Jeff