Delete token error

Hi, i am trying to delete a token but i get the error
{
    "error": 7,
    "reason": "ACCESS_FLAG_ERROR"
}
this is returned with this http request
https://hst-api.wialon.com/wialon/ajax.html?svc=token/update&params={"callMode":"delete","h":"my_token","fl":-1}

and with this

https://hst-api.wialon.com/wialon/ajax.html?svc=token/update&params={"callMode":"delete","h":"my_token","fl":-1}&sid=my_sid

i get this error
{
    "error": 7,
    "reason": "CHECK_TOP_ACL_FAILED"
}

does anyone have an working example of how to delete a token?

thanks in advance!