HTTPCallout.cls

HTTPRequest hr = new HTTPRequest();
hr.setEndpoint('callout:Bank/accounts/DynamicsCorporation?accountType=Checking');
hr.setMethod('POST');
hr.setHeader('Accept', 'application/json');
hr.setHeader('Content-Type', 'text/plain');
hr.setTimeout(120000);

HTTP h = new http();

String responseBody = h.send(hr).getBody();
system.debug('response : '+ responseBody);

Map<String,Object> m = (Map<String,Object>) JSON.deserializeUntyped(responseBody);
for(String key: m.keySet()){
    system.debug(key + '=>'+m.get(key));
}