The body attachment occurs if you fail to show up in court to answer questions. You are not jailed for the debt, even if it feels that way. Folks often respond to the court notice, show up and explain that they are broke, and then leave. It is the failure to obey the court order that gets you in trouble. I wrote about this topic, a few months ago. Follow the link, below.
No. You can be picked up for refusing a court order to show up for a hearing or debtor's exam in some cases, but not for the debt. Debtor's prisons were abolished a long time ago. Your creditor has the option of garnishing your paycheck or bank account, unless you only have exempt funds in the bank account.
$300 isn't a lot of money, but if you have other substantial debts then my firm and many others in the area could help you deal with those creditors on better terms.
If a collector threatened to have you arrested because you did not pay a debt, you should contact a qualified consumer attorney in your area for violations of the FDCPA.