Coppersmith's method for small public exponent
If you only know the ciphertext and the public key, you should not be able to do anything, since RSA is intended to  be used that way.

However, here are some leads which may help you to recover your message (since $e$ is low):


If the same message (with the same padding!) have been sent to $e$ different people (hence encrypted with $e$ different public key), you can recover the message using the Chinese Remainder Theroem. This is known as Hastad's broadcast attack.
If the message is short and not padded, you may be able to recover the message simply by taking the $e^{th}$ root of the ciphertext. Note that it can only work if $m^e &lt; n$.


In a more general way, I invite you to take a look at Dan Boneh's "Twenty Years of Attacks on the RSA Cryptosystem" namely the section about low public exponent.