Unless there is more to this, you have no claim against your employer. You may disagree with its decision, but unless they termianted your for a discriminatory or retaliatory reason, you have no claim. If the receptionist is lying for discrminatory reasons, you could have a claim, but more information woudl be necessary.
If you are an employee at will, then you most likely do not have a claim against your employer. Generally speaking an employer can believe one employee's version of events over another employee's version, even if the employer believes the wrong person.
But if you have an enforceable employment contract, or if you are a member of a union, or if you are employed by a government, you may have remedies to pursue.
Meanwhile, you should file for unemployment if you are eligible and pursue your COBRA rights regarding health insurance.
You may have a defamation claim against the receptionist, through that may not be worth a lot.
This response is merely a general discussion of an issue based on the information provided. It is not intended as legal advice and does not form an attorney-client relationship. You are encouraged to seek out an attorney of your choosing in your local jurisdiction, and to discuss your legal issue with that attorney.